Immigrant Visa eligibility for my Brothers daughter who is turning 21

Only if she is saved by application of the Child Status Protection Act.

One of the vendor has provided us a fake H-1B copy of his employee, Any legal actions can be taken?

You could notify the USCIS of the wrongful activity and the vendor could be debarred from filing H-1B petitions in the future, among other penalties.

Immigration Law - Dream Act: Will a misdemeanor DUI affect chances of being approved for Dream Act/ deferred action?

Yes, however USCIS may honor an expungement in these limited circumstances. Consult with an attorney.

Father of my kids has an immigration hold over a case he had in 2013. Would he be deported right away?

If he is in removal proceedings before an immigration judge, he may assert any defenses or relief applications that he may have available. Consult...

Can fraudulent marriages go on someones record or be documented to immigration if they have a history of marrying for greencard?

Yes, these can become a part of a person's record and can subject them, to severe immigration and criminal penalties.

How can I stop my wife's petition for her alien parents?

No. You cannot affect your wife's petition for her parents.

Misrepresentations never really slip through the cracks, since USCIS will ask about any previous misrepresentations later.

Stamping of f1 while traveling back from home country

Any travel requiring an application for a new visa can be a risky proposition and discussion of all relevant facts is warranted before making such...

Immigration

If the marriage is no longer viable, you will need to seek a waiver of the joint filing requirement. You cannot file under the "good faith waiver"...

Yes, there are many programs in which military members and family are afforded preferential treatment in the US immigration law.