Impurity on body, clothes or place of Salaah

Q: If a person is praying at home on a clean floor, should he still spread out a prayer mat to pray on, or would this be unnecessary since the floor is clean? What would be the best for him to do in this situation?

Q:

1. If I place a clean musalla on an impure carpet can I pray on that musalla?

2. Also, if I make wudhu and then stand with my wet feet on the musalla that is on the impure carpet will the musalla become impure since the water penetrates the musalla and goes to the carpet or will it be pure. Because I heard a masala that if you wrap a wet impure cloth inside another cloth the other cloth won't become impure.

Q: Is it permissible to pray wearing shoes? Because I've read a hadith that it is permissible so I just wanted to clarify it.

Q: My question is if clothes becomes najis after the salaah and it was clean during the salaah will the salaah have to be repeated?

Q: I sometimes find after performing Salaah, a little dirt under my nails. Most often my nails are short. What will be the condition of my Salaah? Is it valid?

Q: Thew new £5 UK note is made of plastic and contains animal fat. Can one pray salaah with this note in their pocket?

Q:

1. Is it permissible to use the new five pound notes as they contain animal ingredients?

2. When praying Salah by having the £5 notes in the pocket will the Salaah be valid?

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: 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: Could Mufti Saheb please tell me if Salaah should be repeated if one carried a child and afterwards found his clothes to be damp. Thinking the dampness to be sweat he performed Salaah. After that he found that the child's diaper had leaked and it had not been sweat.