Can I post an immigration bond for my wife if there is an ICE hold?

You can always ask, but the standard procedures is that they will not make any decisions until they have her in custody.

Can I work for employer A again if I have initiated a h1 trasfer to Company B and started working for them?

Co. A would need to do a new H1b transfer for you to return to them, once you go to company B.

Can i still file for the Deferred Action for Childhood Arrivals application even if im in Mexico?

No, you have to be in the U.S.

Do I need to file DS-260 online?

Either one of you can submit the form online.

My previous company is not providing me an experience letter, what are my choices?

You can do an affidavit about the work you did, or have a co-worker do one.

About citizenship

You will need 5 years permanent residence to file for citizenship if you are not married to a US citizen.

How long can I stay in US after my H1B Visa and I94 expiry, even though I have applied for extension and received my petition no

You can stay in the US as long as the application is pending. Call customer service about the new address.

Dear, my sister applied for me in 2012 for the green card I-130, in 2009 I received the letter saying it is on post decision.

About 6 - 7 years.

Perhaps you do not have a winnable case. Speak with a lawyer who can evaluate the facts.

Can I apply for a green card after been convicted of passport fraud and served 8 months in a federal prison?

There is a waiver for crimes under section 212(h) and (I) of the Act.. You can file your adjustment with form I-601, to request a waiver. If you...