Query Regarding ITR 1&2

Dear Sir,

please reply to below query.

1. A person have income from salary approximately Rs. 5 Lacs from three employers. he alwsys filed ITR-1 but FY 2023-24 have also income from short term capital gain Rs. 3457/- (Mutual Funds) so i think he is eligible for ITR-2 Can he file ITR-1 or show capital gain under income from Others sources.
2. All employer not mainted books of accounts and not registed in GST filed ITR 4. One employer paid salary by banking channal and rest both emloyer paid salary by Cash Rs. 20000/- and Rs. 8000/- so ITR 2 we need to mention employer wise break up. so Can emloyee face any issue from depaetment.
3.Person have some other income Rs.19560/-computer training to students so can he show under income from other sources while filling ITR
4. Person have saving account in post office so he is unable to update account in it portal due to ifsc code so can be any issue.
Please advise Sir,