Is it permissible to convert a restricted vow that has not been fulfilled into an unrestricted vow, and is it obligatory to fulfill it after conversion?

Undertaking a vow (nadhr) is disliked, but if a person makes a vow, it becomes obligatory to fulfill it if it is an act of obedience. A conditional vow does not have to be fulfilled until the condition upon which it is dependent occurs. If one fulfills it before its realization, the majority of scholars (Malikis and Hanbalis) hold that it is sufficient, and the Shafi'is also hold it sufficient if the act of worship involves wealth, while the Hanafis believe it is never sufficient. A vow cannot be revoked once it has been established.