Do I have to give back the money paid to me by a company?

You need to speak with an attorney. I don't know whether you have a valid claim for severance or vacation, but if it was paid to you in error, and...

I was asked to sign an NDA and I did, but they didn't disclose that the previous agreement with them was over.

Without reading the document and asking you further questions, there is no way to respond. Take the document and consult a local employment attorney.

Made to resign from work

They can't "make" someone resign. I suggest your friend speak with an employment lawyer and give all the facts.

I was hired as a employee to set tile by a contractor in Las Vegas Nevada are home owners responsible if contractor wont pay?

No. The homeowner is not your employer.

Is it legal for your employer to video tape or record you outside of work

From what you said, it sounds like there is no proof of videotaping, just people observing.

Actionable hostile work environment is either sexual, or based on a protected class (discrimination).

Where do I start for negotiating a settlement in a racial discrimination lawsuit?

You can't just pick a number out of the air for what you "want". What are your actual damages?

Unemployment benefits

Obviously I have not reviewed the evidence. Apparently they found the employer more credible than you.

What can I do if a company offers me an internship position but fails to hire me?

Contact their HR, or your contact with the compnay, and ask for an update.

Racial/national/disability discrimination, sexual/gender harassment and physical attacks. EEOC right to sue 6/6/16.

If the EEOC issued a right to sue letter, you better start speaking with, and retain, an employment attorney. Your clock is running.