Yes you can change status from J1 to B1/B2. Yes you can stay in the U..S. while it's pending. Yes you can file for a green card if you marry a...

You need to have between two years of post high school training, or a bachelor's degree.

You have to be a parent or guardian.

If there is none, you do not need to write anything at all.

If she has not aged out and she is in the U.S. in lawful status, she can file for adjustment in the U.S.

It depends on what application they have pending.

The U.S. does not regulate your work outside of the U.S.

Majority of the time must be in the U.S. and must not be any break in continuity.

If she is under 21, and lawfully admitted to the U.S. , she can file an i-485 based on her pending I-130.

The passport expiration date, or whatever date beyond that is allowed by treaty with your country and the U.S. Forget about 2025.