Conditions for the validity of Salaah

Q: I want to know if a man's trouser is minorly torn at different places, can he perform prayers or do dua?

Q: I've prayed Salaah with a garment on many occassions and just recently discovered a hole in it slightly above the knees. Since the male awra is above the knees does that mean all of those prayers were invalid, and do I have to make them up? Also do skinny jeans invalidate salah since they show the shape of the legs?

Q: I heard that praying fajr after sunrise is an act of shirk. But what if I accidentally prayed fajr 2 minutes after sunrise without knowing it was past the time for fajr?

Q: Recently I performed two Salaahs at a jamaat khana. However the next day I realised my underwear was soiled. What should I do?

Q: Can I read Fajr namaaz after Azaan without waiting as we read maghrib?

Q: Is namaaz valid in half sleeve shirt?

Q: What is the definition of twilight? In beheshti zewar English it says the redness on the western horizon, when that disappears then esha time comes in. However some kitaabs mention the twilight according to imam Abu hanifa as the whiteness after the redness. Which is correct. Why is it mentioned as redness in the beheshti zewar, would this not make our esha time early like the shafis etc.

Q: What is the definition of sunrise/shurooq? When the sun slightly appears on the horizon or when the sun completely is visible on the horizon?

Q: I performed Salaah not knowing that there was mazi on my clothes. It was only a few hours after performing the Salaah that I realized that my clothes has been soiled. Is that Salaah valid or do I have to repeat it?

Q: Upto how many minutes before Ghurub aftab, Salatul-asr can be prayed and how many minutes before ghuroob aftaab, makrooh time for salatul asr starts?