Clothing and Covering the Aurah

Q: Is salaah valid when one is performing salaah individually at home while wearing pyjamas or other night attire?

Q: Does the area starting from the chin need to be covered during salaah for women?

Q: If the dress or skirt of a Hanafi woman is above her ankles (i.e. the ankles and part of her shin are exposed), will her salaah be valid if she prays salaah after putting on socks to cover the exposed area?

Q: Is it mandatory or necessary for women to wear something under the gown (like to wear a shalwar or pants under a night dress) in order to perform namaaz or can she read her namaaz just wearing the gown or night dress which covers the whole body up to the feet but nothing inside. Will her namaaz be valid?

Q: If a person prays while wearing a t-shirt that has depictions of creatures on it, is his prayer valid or should he repeat it?

Q: If a person prays with his t-shirt inserted in his pants, is his prayer valid or should he repeat it?

Q: Is wearing a skull cap mandatory whilst praying Salaah?

Q: Can we perform salaah with clothes on which has animals like Puma shirts, etc.?

Q: I wear a trousers belt, it's leather. I don't know what kind of animal skin was used to make this leather belt. I heard that if you wear leather made with pig skin and if you pray salah with it, it wouldn't be accepted, it's nearly impossible to tell if the leather is pig skin or not because where you buy it, it doesn't says. Would my salah be valid? 

Q: Can we wear a leather belt in namaaz or not?