Is Maghrib prayer valid if prayed individually, separate from the missed Dhuhr and Asr prayers? And is it permissible to delay making up missed prayers until the following day?

The one who sleeps through a prayer or forgets it is obligated to perform it when he wakes up or remembers it, based on the Prophet's (peace be upon him) saying: "If one of you oversleeps or forgets a prayer, he should pray it when he remembers it, for Allah says: 'Establish the prayer for My remembrance.'" There is a difference of opinion as to whether missed prayers should be performed before the current prayer as an obligation or a recommendation. If one prays the current prayer before the missed ones, his prayer is valid, but it is preferable to make up the missed prayer first. It is not permissible to delay making up the prayers; rather, one must hasten to make up the prayers and repent to Allah.