B1 Visa to F1 Visa conversion

Yes. A lot of factors (you must be in status, program based on I-20 must start before expiration of your current status, financials etc.).

Getting GC while on h4?

Will the employer continue with the I-140 though?

When changing jobs (old job-EB3) and applying for EB2 can I use same priority date?

Yes, Yes, and Yes unless the I-140 was revoked.

I-130 supose of us citizen

Consular processing cases are pretty slow these days.

Re-entry

If you show your intention to return to your home country anyway, should be fine. But every time someone uses up most of the 6 months period, then...

Just say you have various red light violations. You’ll be fine. It’s a traffic violation only.

Adjustment of status

Depends on caseload of Judge. IH may be scheduled a year or so from now, whereas if you go the termination then CIS route, 3 months from 485 filing...

Does not going to school make me I admissible of obtaining green card?

Might be a problem if you did not go to school at all.

Do I have to prove my OPT jobs when applying for a green card by marriage, or just my I-20 is enough?

Marriage to US Citizen? As long as you entered legally you’re fine. IF they ask for those things you mentioned, which I doubt, then it’s pay...

It been 95 days after n400interview nothing yet what is going on

Sometimes if there are issues it takes longer.