Prayer

If you and him were in the position of ruku at the same time, this is a valid Rakah even if you didn’t recite the Fatiha.

No, as you seem to be an OCD patient. You have to ignore such thoughts and wiswas.

You must not do this as a habit. Try to offer the prayer earlier. However, if you prayed one Rakah before the sun began to rise, your prayer is valid.

Of course it must touch the prayer mat.

Kindly follow the link given: https://www.assimalhakeem.net/should-i-do-rafadayn-or-noti-e-raising-hands-before-and-after-ruku-and-in-the-starting-of-third-rakah/

If he missed them without a legit reason, he cannot make them up. If he had a valid reason, he prays them as the order goes (asr, maghrib, isha).

If you realized that you are in the 5th, you must immediately sit for tashahud without continuing the 5th. You must offer Salam after the two forgetfulness sujood. However, due to your ignorance, your prayer is valid.

This is according to the shafiee math’hab and it is wrong and not according to the sunnah. However, one may raise his hands and say AMEEN.

The prayer is valid if you do not hold or fold your hands but you lose reward for not following the sunnah.

Yes