Do I need to repeat Namaz if I do sajda sahu when it wasn’t wajib?

1. Sometimes i miss something in Namaz, So not knowing that sajde sahu is wajib in this condition, I used to do sajde sahu. My question is that, if a person do sajda sahu in Namaz and later realizes that it was not wajib on him so do he need to repeat that Namaz. 2. If I recite same surah multiple times(in different Rakats), is Sajda sahu wajid on me? 3. If I have joined a jamaat but miss some rakats so i have to stand up as Imam recite salam, But I forgot to stand up, and also recite salam on one side or both side, Is sajde sahu wajib?? 4. If i forgot to reaise the finger in Tashahaddud, Is sajde sahu wajib?? 5. If I forgot to do Niyah, do I need to repeat the Rakat. 6. Imam was doing Qiyam, I joined him by raising the hand but forgot to say Allahuakbar. 7. If I joined imam while he was in Ruku, I Had qiyam for a time equal to 3 Subhanallah, and joined Imam but before reciting anything, Imam goes to Qauma, Can that rakat countable??