Is it true that he wont get card for 3 years because of the age was 20 years and 5 months of 21?

Your co-worker really should bring his case to an attorney for a proper consultation.

1. What are the chances of getting B2 Visa: with or without I-130 filed ? 2. Can I apply for I-130 with I-551 ?

She will not get a visitor's visa, because she is an intending immigrant. Consult with an attorney.

Arrest record afted for I 751 issuing green card

Yes, any criminal conviction could affect your immigration status.

We want to open an office in U.S. to conduct liaisons here to find investors in our energy projects abroad. Is L1 visa possible?

The L-1 visa is not appropriate if the purpose of the worker's presence in the US is solely to act as an "agent" of the foreign related entity....

Paying US taxes when working and living abroad

I would recommend that you consult with a tax attorney on these questions.

Can you travel to mexico if you have a previous felony but are now off parole?

If you are not a citizen of the US, any foreign travel could result in a referral for removal proceedings.

How can i reapply so that visa will approved?

They would need to demonstrate strong ties to the home country to persuade the Consul that they are intending to depart after their stay.

What can i do from my situation and is there any other option to live and work in USA?

Your brother cannot petition for you until he is a US Citizen and even then, it would take many years to immigrate. Perhaps your brother should...

What should the income be before bringing a fiancé to the US from another country?

It depends on how many dependents you already have, including any other people you may have sponsored on an affidavit of support in the past.

Yes, your application is still considered "pending" for EAD purposes.