Why Shiva does not worship anybody where as Vishnu worships him in all incarnations?

There is a difference between Bhagwata Purana and Shiva Purana,

A. Bhagwat Puran states that Vishnu is supreme one than Shiva, and From Vishnu, Brahma and By Brahma , Shiva was born but if it so, why Vishnu worship Shiva in all of his incarnations, where as Shiva never worships anybody.

B. Shiva Puran says that Vishnu and Brahma were created from Aadi Anant JyotirStambha of Shiva. When there was a dispute between Brahma and Vishnu about who is the supreme, at that time Shiva appeared as Jyotirstambha and asked both of them to reach start and end of it. Vishnu traveled downwards to reach end and Brahma traveled upwards to reach beginning, but both of them failed and considered there is no end of Shiva and asked Shiva to guide them. In this story Brahma lied that he reached beginning, So Shiva banned his worships in Hinduism, which is true. Brahma's son Daksha Prajapati was against Shiva because of this reason only.

Now, Lord Rama established Shiva Linga when he was marching towards Lanka which is known as Rameshwara Mahadeva means Ishwar(God) of Rama.In Ramayana when Lord Rama wanted to do Prashchatap because he considered killing Ravana as sin of killing a brahmana, he asked Hanumanji to organize to establish a Shiva Linga and asked again Shiva for mercy and to cut his sin. If Lord is himself able to cut sins, Can't he cut his own sins?

In Krishna avatar when Krishna wanted to bring some tree kalpa Vriksha from Indra, he worshiped Shiva for blessings and that is known as "Gopeshwara Mhadeva" in vrindavana means Ishwara (God) of Gopal(Krishna). Also when Krishna wanted to have a son, he asked sages and from their advice he prayed to Lord Shiva to get a son. If Krishna was Vishnu against whose will nothing happens, why he said that "Shive Sarvadhi Sadhike" means nothing happens without Shiva's will, so please bless me with son!! when the Mahabharata was about to be battled he asked Pandavas to have bliss of Shiva first and arranged a Pooja of Shiva Linga...

In Bhahwata Puran also the story is stated about Lakshmidevi's unhappiness with Vishnu because Vishnu told her that in his half area of heart is dedicated to Lord Shiva only. And in the rest of half, all the creatures of world and all deities including her wife Lakshmi lives!!

Parshurama is considered as great devotee of Shiva, Shiva gave him Parshu, for which Parshurama is famous for.

Why Shiva does not worship any body where as Vishnu worships him in all incarnations?

What I think is because Shiva is the only supreme Paramatma as he is unborn(Ajanma), Akarta and Abhokta(Vairagi) as said in Geeta that GOD is Ajanma, Akarta and Abhokta. God is neerakar (Shapeless and formless), Shiva Linga is symbol of Shiva 's such form only.

And also Vishnu always advised other deities(Kartikeya, Indra, Parvati,..) to worship Shiva only if they have mistakenly committed sins.

But now it is curiosity to know about this. Can anybody put light on my doubts?

Vishnu says Shiva is eternal origin(seed) of all things

From The Mahabharata, Anusasana Parva -> Veda Vyasa Mahabharata

The blessed Vishnu said: "I salute Mahadeva. Salutations to Thee. O Thou that art eternal origin of all things. The Rishis say that Thou art the Lord of the Vedas. The righteous say that Thou art Penance, Thou art Sattwa, Thou art Rajas, Thou art Tamas, and Thou art truth.

Vishnu himself said "Shiva is eternal origin of ..." That's why Shiva linga is seed and Whatever we see it is just a tree from that seed.

Story of origin of Godavari river

The story of the Godavari river is told in this excerpt from the Kotirudra Samhita of the Shiva Purana. In this account, the sage Gautama, who is a mind-born son of Brahma, is engaged in Tapasya (deep meditation) on the Brahmagiri mountain when there is a hundred-year drought in the area and thus crops can't grow. So for the welfare of others, he starts engaging in Tapasya to Varuna the ocean god, who appears before him after six months. Varuna denies Gautama's request for rain, because it would go against the wishes of the gods, so Gautama instead asks for "divine everlasting water yielding permanent results." So Varuna tells Gautama to dig a ditch, and then Varuna fills it with divine water and says this:

O great sage, let there be a perennial supply of water in this ditch that has become sacred. This will becomes famous on the earth by your name. Charitable gifts made here, rites performed here, penance pursued here, the sacrifices done here for the gods, and the Shraddha offered here to the manes, everything will be imperishable.

So Gautama and other sages in the area come to the new body of water and start planting crops and the like again. But on one occasion, Gautama sends his shishyas (disciples) to get water, but they're stopped by the wives of the other sages, who want to get water first. The disciples complain to Gautama's wife Ahalya, who goes to the body of water and collects water before everyone else. The other sages are furious at this petty incident, so to get revenge they pray to Ganesha, who appears before them. The sages ask him to force Gautama to leave his hermitage; Ganesha first advises them not to try to harm someone who has only done them good, but they insist.

So Ganesha approaches the sage Gautama, taking the form of a feeble cow, and starts eating Gautama's crops. To shoo the cow away, Gautama throws some blades of grass at it, but as soon as the grass touches the cow he sees it fall dead. Gautama is shocked that he has committed Gohatya (cow-killing), a supreme sin in the Hindu religion, so he takes his wife and leaves the hermitage in order to undertake an arduous course of repentance that involves circumambulating the Brahmagiri mountain, going around confessing his sin to everyone he encounters, and making Lingams to worship Shiva.

Finally Shiva appears before him, and Gautama asks to be made sinless. Shiva laughs and says that Gautama hasn't committed any sins, and that Gautama is such a great sage that even looking at him makes other people sinless. In any case, Gautama asks Shiva for Ganga to be brought there, so that he and others could be purified of their sins. So Shiva gives Gautama "the essence of the earth and heaven" (whatever that means), which was apparently Gautama's inheritance from his father Brahma, and I guess Gautama uses that essence to summon the goddess Ganga. Shiva tells this to Ganga:

O goddess, till the advent of the Kali Yuga, when the son of Vivasvat shall be the twenty-eighth Manu, you shall stay here alone.

I think this is a scrambled translation, by the way; there are only 14 Manus who rule in a given Kalpa, not 28. It probably means "till the advent of the 28th Kali Yuga, when the son of Vivasvat shall be the Manu", because the current Kali Yuga is the 28 Kali Yuga of the Vaivasvata Manvantara. And it probably means the end of the Kali Yuga, not the beginning, because the Godavari river is still here.

In any case, Ganga says that she'll only agree to stay if Shiva also stays there, so Shiva manifests himself as Tryambakeshwara (meaning the three-eyed lord), one of the twelve Jyotirlingas (Lingas that appeared after Shiva manifested as a pillar of light.) Here is a picture of it:

So Ganga agrees to stay there as a new river, initially called the Gautami river but now known as theGodavari river. Gautama and his disciples bathe there to purify themselves of sin. And even the sages who tried to take revenge on Gautama are eager to get rid of the sins. Ganga is initially reluctant to purify these men who had been so cruel to Gautama, but then Gautama convinces her to relent and he digs a ditch for her to emerge from and purify the sages of their sins. That ditch is the famous Kushavartha Thirtha at the Tryambakeshwara temple.

On a side note, like many parts of the Shiva Purana, at least some of this account seems to be a later interpolation, because it apparently references the Pachayata, a group of five gods who are worshipped in the Smartha sect founded by Adi Shankara, so it's an anachronism. Also, the reference to Ganesha may be a later interpolation, because references to Ganesha in the Mahapuranas are few and far between.

You may also be interested to know that this apparently isn't the first universe that had a Godavari river in it; the next chapter of the Kotirudra Samhita of the Shiva Purana gives an account of how a similar story occurred in a previous Kalpa.