Hi.Sriram,
Restricting to edit infotype personal data and others can be done via authorization using athorization P_PERNR .
you can restrict upto personnel area, infotype, subtype, employee group employee sub group not beyond that field leave auth is not possible. but you can do one think.
if you want to hide or making metndatory of fields in a infotype for deferent deferent usesr then you can achive this via feature "screen control" ex. feature P0002 (personnal data screen control).
so which will be reflect in portal.
but i think this is not your requirement
Regards,
Dinesh