Conditions for the validity of Salaah

Q: How is it to perform salaah wearing a T-shirt?

Q: We are Hanafi. If I am leading the salaah at home, and my wife wants to read salaah behind me. What intention should I make? E.g. during ramadhaan, I read Esha, Taraweeh and Witr. Do I need to make an intention for each two rakaats that she is behind, or can I make an intention once for Esha and let it count for all. How must the intention be made? Verbally, in the mind, or just a realisation that she is behind me?

Q: I follow the Hanafi fiqh and the time for Asr salaah is at 6pm but I live in a city in which we only have one musjid and they read asr at the Shafi'ee time of 5:15pm. Is it okay for me to read asr with Jamaat according to the Shafi'ee fiqh even though I follow the Hanafi fiqh?

Q: I have heard that Salaah is more makrooh when our trousers (pants) are folded up during Salaah? Please advise with the reference from Hadith.

Q: Is one allowed to change one's niyyat of Salaah (during salaah) from Fardh to Qadhaa?

Q: At work sometimes there isn't enough time to pray Asr before closing. Is it possible for me as a female to pray my salaah whilst the azaan is being given.

Q: After wudhu can ladies wear lipstick and read namaaz or before wudhu?

Q: At the ground where one places his feets during qiyaam, there is less than a dirham najasah and one notices this after salaah? Is the prayer valid?

Q: 

1. Is it permissible to perform Esha salah according to 12 degrees as mentioned in Ahsanul Fatawa and is the salah performed valid?
2. Is it permissible to perform Fajar salah according to 12 or 15 degrees and is the salah performed valid?

Q: Is namaaz makruh if the jubba does not cover the elbows?