durood-e-ebrahim

Mistake in Attahiyyaat and Durood-e-Ebrahim

Q:

1. If one happens to omits portion of Durood Ibraaheem due to one forgetting it or making a mistake, is the Salaah valid?

2. If one happens to recite Tashahud and one repeats the portion( Ash Hadu...) where the index finger should be raised, perhaps due to getting stuck, should one raised the finger twice?

3. If yes, and it was not raised twice, is the Salaah valid?

4. Whilst in Salaah, during Durood Ibraaheem, one adds the words "Sayyidina" before the words and Names Muhammed (Sallallahu Alaihi Wassallam) and Ibraaheem (Alayhis Salaam), is the Salaah valid?