What is the correct Sunnah regarding Tarawih prayer, what are the bid'ahs (innovations) introduced into it, and is it legislated to make supplication collectively after Tarawih prayer?

The collective supplication (Du'a) after the Tarawih prayer is an innovation (Bid'ah) and was not reported from the Prophet (peace be upon him). He said: "Whoever performs an action that is not in accordance with our matter will have it rejected." What is reported after the Tarawih prayer is to say: "Subhanal-Malikil-Quddus (Glorified is the Sovereign, the Most Holy)" three times, raising one's voice on the third repetition.