What is the ruling on the Qunut in Witr prayer before the Tasleem, and what is the ruling on supplication during prostration in general, and specifically with written supplications circulated on Islamic websites?

Supplicating after the tashahhud and before the taslim is legislated, based on the Prophet's (peace be upon him) saying: "Then let him choose whatever supplication he likes best and supplicate with it." It is permissible to recite the Qunut supplication at that time, but one should not do so continuously so that it does not become like a Sunnah. Supplicating in sujud (prostration) is recommended, based on the Prophet's (peace be upon him) saying: "The closest a servant is to his Lord is while he is in prostration, so increase in supplication." It is permissible to supplicate with written supplications if they are free from any prohibitions, but it is preferable to supplicate with the ma'thur supplications (those transmitted from the Prophet, peace be upon him).