Will USCIS take 90 days to approve EAD renewal after L2 visa extension is approved?

It should not take 90 days or more. If everything has been done properly, maybe 30 days.

Whenever there are such serious concerns involved, I always suggest contacting an immigration attorney.

Can I change the employer when my petition is under RFE?

Whenever there is an RFE involved, I always suggest contacting an immigration attorney.

My company is willing to sponsor me for a green card, what are the things that i need to do now?

You need to ask your employer to get you in touch with the lawyer who will handle your case.

You will encounter problems possibly if your fingerprints were taken.

Looking for a specific J1 visa which allow me to work in a company and do research at school cuncurrently?

Have you reached out to your employer's attorney on your case?

Asylum was denied?

Whenever there is a denial involved, I always suggest contacting an immigration attorney.

You need to contact an immigration attorney to discuss the specific circumstances of your case.

I bonded an illegal who then filed a PFA/no contact against me, can I cancel bond

You're definitely in a bind. However. certainly, an illegal alien also deserves to be safe. Your best be is to file for modification of the pfa and...

I'm a musician in Australia with a US fiancee, Am I able to work in the USA ( do gigs a venues, sell my show etc ) ?

Even if your partner sets up an entertainment company, you still have to qualify as an Extraordinary person. Consult an attorney.