Not a good idea for the reasons the other attorneys stated.

There is still time left on the premium processing clock to get an approval. Good luck!

Can my employer in India do anything to harm my L1 A visa ?

I would speak to the management first because as the other attorneys stated, this could be an issue for your immigration prospects.

If I switch jobs while my spouse's greencard application is processing, will that likely cause problems?

It shouldn't - as long as you can afford to support your spouse a job change doesn't matter.

Attorney Samuel is correct - congratulations on your naturalization!

What is my current status?

You are an adjustment applicant in a period of authorized stay.

Can my spouse apply H4 for me in the above scenario ? Can I stay in US ,once my H1 is rejected and application for H4 is on ?

He can but the timing will be critical - talk to the company attorney for more information.

Can I apply for F2 while my h1b is in process?

Yes you can apply for F-2 but continue to monitor the H-1B.

Which date counts for 30-day grace period? Does the J1 sponsor have the authority not allowing me the 30 day grace period?

The sponsor cannot change the 30 day grace period.

I am convicted Green card holder in 1993 can i apply stand alone 212c

You need to have your entire file reviewed by an attorney - this forum is for general questions only.