Very typical question related to mutual agreement of divorce

The case is like this ; husband and wife were living separately from last 3 yrs -a child(boy) aged 6.5 years is living with mother,mother filled all cases,498a,406,dv but after 1.5 yrs of case wife got ready to take mutual divorce and a mutual agreement on stamp paper duly notary attested was made on which wife agreed to take all cases back and husband also agreed tht child will stay with mother forever and husband will not apply for any custody & guadardianship under any section in any court in future . This mutual agreement along with mutual divorce petition was submitted in family court,now the court has given decree of divorce and have mentioned in order just 1 line about child that child is living with mother and will live with her in future - thats all . Now can that father apply for visitation ? Can that father go for custody ? Can that father go against that mutual agreement ? Can that wife file 420 against father if he files a visitation or custody case in court that husband is commiting fraud by going against a mutual agreement ? Can that wife go for quash of petition if father applies for visitation or custody in family court , if yes than under what section can wife apply for quash ? Under rule of estoppel can wife file any case against father , if yes - under which section .. Pls advice as this is tricky situation . Thanks