Why is it so hard to obtain a green card?

If you Barry a USC it takes only 4 months on average.

Born in mexico city raised in S.F CA. I am 21 my dad was a US citizen before i was born he past away but never claim as his son

You need to hire an attorney to help you with this. Very complicated

Born in mexico city raised in S.F CA. I am 21 my dad was a US citizen before i was born he past away but never claim as his son

You need to hire an attorney to help you with this. Very complicated

I came az fiancé I marry after 1years apply for green cart they accept me bcz I should marry before 90days any way for me stay

Ok. So what was your question?

Divorce here. Has no effect on immigration.

If I let my H1B expire and go to EAD, can I renew my H1B later if necessary or I will have to get a new one through the cap?

No. You would have to exit the us.

What should I do if I don't remember the date of my citation to write in N-400 application?

Get as close as you can and write approximately.

Student Visa ?

Be accepted at a school. Get an I-20 and apply for a visa at an embassy. Not harder but you have to be eligible.

Husband's L1B visa expiring in Aug 2012.His I-94 is upto 2014.He has completed 5 years of stay allowed on L1B visa.

Can't tell. Would need to examine the history. If he has the 2014 i94 he should be ok. All l visas are not 5 years. Some are 7

What happens if i get separated from my spouse after joint filing I-751 before the case is approved but extra evidence asked?

You need to tell immigration what is happening as they will catch you in a lie later on. Best to seek the advice of an attorney right away.