(1 & 2) If the things which Zaid gifted to his wife during his lifetime was common between Zaid and any other one i.e. the son living with him and they were distributable but Zaid gifted it without dividing or gifted it after division but did not give it completely to his wife then this gift was not valid as per the Shariah. It is so mentioned in common books of Fiqh. Hence now after the death of Zaid all these things shall turn his inheritance and shall be divided among all his legal heirs. (Shami, Kitab Al-Hibah 8:496 Published Maktaba Zakaria Deoband):
وكما يكون للواهب الرجوع فيها يكون لوارثه بعد موته لكونها مستحقة الرد اهـ
Allah knows Best!
Darul Uloom Deoband