What is the Sharīʿah's view on an inheritance dispute among heirs over a will after they have agreed to it and implemented it for years, and can the Sharīʿah court annul it and re-divide the inheritance?

A will made to an heir is invalid unless the other heirs permit it. If the legatee dies before the testator, the will becomes void. However, if the heirs ratify the will after the testator's death, they are not permitted to revoke it once they have agreed to it and the legatee has received what was bequeathed to him. This is because it is considered a gift, and a gift cannot be revoked once it has been taken possession of.