Documents submitted to USCIS with an application for employment authorization (form I-765)?

No photos must be recently taken for the I765.

Are I-131 and I-765 fees included with I-485 when filing concurrently as of October 22, 2020?

No there are no separate fees if filing with I485.

I-130 for my son taking more than 2 years with no clear reasons

Yes you may consider hiring an attorney to assist with obtaining a decision from USCIS.

How do you get citizenship when brought here as a kid?

Best to have your friend consult with an attorney in private to explore his options.

No not at all especially as your case was approved.

My i-130 is approved and I am within US. Can I file i-485?

It depends on the category of filing whether you are eligible for adjustment of status.

Yes it is possible that they will recapture previous biometrics.

Yes you may divorce in the US but there may be additional requirements by the country where you married.

Yes you may refile for adjustment of status through your current marriage to USC spouse. Consider consult with an attorney for guidance.

Yes a divorce so soon to approval will certainly be questioned at time of renewal.