ITR FORM 3 and 4

As such you can file ITR which is suitable to your nature of income/s. It may change every year, as per the requirement, and there is no harm in its change.

Check whether ITR 4 is suitable as per your income assessment. If yes, you can go with it.

But suppose you have capital gains declaration along with PGBP income, ITR 3 should be opted.