Change of status

I am working on an H-1B visa, and I want to leave my job and join full-time school for a couple of years. I want to start working again using my same H-1B visa when my studies are completed. So, how can I do that by staying within the U.S.?

I am on my STEM OPT, and it is valid till July 2024.

My H1B was picked(March 2022) and approved(August 2022) last year.

However, my H1B was approved under the Consulate processing and received ( I-797 B). So, I asked my employer about it and got to know that I can change to H1 status whenever I intend to or after my stem opt expires.

I am planning to go to India in Oct for stamping. So I asked my employer to change my status to H1B, and they mentioned COS is not needed, I can directly go on STEM OPT and get my H1B visa stamped. It will automatically change the status to H1B.

I am on an F1 visa, and My spouse is on a Green Card. My Green Card through my spouse is under processing(I-130 under Review). I am graduating in March 2024. My questions are as follows:

At what stage in my Green Card Processing can I start traveling outside the USA?

Let us consider my GC is still under processing by the time I graduate and enter the job market:

A)Can my employer file an H1 while my Green Card is under processing?

B)Given my H1 got picked, will there be any issue for me to travel to India to get my H1 stamped?

My sister is in India and the prospective groom is a US citizen. They have concerns about how to proceed with marriage and relocation of the girl to US in a timely manner (prefer not to wait more than a year for marriage/ living together post-marriage for personal reasons) Current fiancé visa processing time seems to be 15 months. It was not this long pre-covid, realistically can this processing time reduce this year? If they do marriage in India first, what’s the quickest way for her to come to US and how long would it take She has a valid B1. Can she travel on that to US post-marriage for 5-6 months only without any risk to her green card application? She is trying to get an L1-B visa through her current company. Will that visa approval be affected if they get married in the meanwhile? In short, what is the quickest path for her marriage & relocation to the US right now?

I am on an H-1B visa and recently got laid off.

If I don't find a job within the 60 days grace period:

1. Can I go back to my home country and keep applying for jobs and then come back once I get one? If yes, would I have to go through the lottery again?

2. If not, what are my options?

3. What additional documents do I need to provide while applying for my new visa to explain the missing pay stubs?

4. What does the company that let me go send to the USCIS as documentation for termination of contract?