What is the ruling on prayer if the Imam is so fast that he starts reciting Al-Fatiha before the worshipper has fully stood up, or if he rises from the second prostration before the worshipper has completed it? And what is the ruling on prayer if the worshipper prostrates on a partially folded prayer rug, or if a part of his garment covers his nose and hands during prostration, or if he prostrates on his niqab instead of directly on the ground? And what is the ruling on saying "Subhanaka" instead of "Ameen Ya Rabb" in the Witr supplication? And what is the ruling on someone who made the takbeer for bowing with the Imam's takbeer out of forgetfulness and then forgot whether he repeated it? And what is the ruling on someone who used to say "Sami' Allahu liman hamidah" while standing after rising from bowing? And do these errors invalidate the prayer?

The issue of not reciting Al-Fatiha behind the Imam is a matter of scholarly disagreement. Your prayer is valid according to the majority opinion, even though the fatwa (religious ruling) given is that its recitation is obligatory. Your prostration on a folded prayer mat is valid, and saying "Amen, O Lord" or "Glory be to You" during Qunut does not invalidate the prayer. Synchronizing with the Imam in ruku' (bowing) is disliked but does not invalidate the prayer; the Sunnah is for the worshipper to perform the actions of prayer after the Imam. Doubt about omitting takbirat al-intiqal (the transitional takbirs) does not affect the validity of the prayer. As for saying "Allahu Akbar" after fully standing up, this is incorrect; the correct practice is to say it while rising from ruku', but this does not invalidate the prayer due to ignorance or forgetfulness. If you are behind the Imam, you do not say "Allahu Akbar" at all; rather, you say "Our Lord, and to You be praise" while rising from ruku'. The draping of the garment over the face or hands, and placing the hands on the niqab during prostration, do not affect the validity of the prayer.