Hello Saurabh
Not sure as you seem to have done the correct settings, but can you please re-check your conditions relating to authorisations on the fields? E.g. whether this is changeable by certain groups (auth.) or whether under any of the conditions this field is still editable. Might be that you as creator or the Project have admin access which fulfils a condition that makes this field editable. Understand what I mean? Differently put - have you checked on other users that they also see the fields as editable?
Regards
C