All age-out cases have been indicated to be first priority. For CSPA, only relevant consideration is the time needed for I-130 approval.

Your friend may apply for B 2 visitor visa. During the interview you may provide an invitation letter to support her visa.

Student status is not a job. You may list other employments even if they are for brief period of time.

School employment is of course a real employment.

You should file the form I-130. Once I-130 is approved, he will be able to apply for an visa through local US embassy. you should consult and hire...

You should provide amended tax return only along with 2020 W2 and recent paystubs and job letter. Tax transcript is not essential.