1- What is correct concerning the hadith whose origin is unified and which was narrated by a group through the same chain, and one of the trustworthy narrators added an increment: is this increment considered an "increment by a trustworthy narrator" or "anomalous"? 2- When do I raise my hands when standing up for the third rak'ah (for me) in a four-rak'ah prayer where I caught the Imam in his second rak'ah?

An increase from a trustworthy narrator is accepted by the people of knowledge if it does not contradict what was narrated by trustworthy narrators. As for the anomalous (shādhdh) narration, it is when a trustworthy narrator contradicts more trustworthy narrators. Whoever catches the Imam in the second rak'ah should follow him in all the actions of the prayer, including raising the hands when standing up from the two rak'ahs.