Yes, if you have filed Form-20B earlier then you can file revised Form-20B with ROC. But ensure that the details of earlier Form-20B and reason for revised Form-20B must be given in revised Form-20B.
Yes, revised filing of all Annual filing eForms except Form 23AC/ACA can be done in respect of the Forms already filed but the fees for subsequent revised filing shall be charged, assuming it as a new filing.