Questions about modeling

1)What programs must i have to start modeling?(free please)
2)How do i start modeling?
3)How do i make parts ragdolled?(like tanks)
4)How do i make a good texture?
5)How do i port models?
6)How do i make bodygroups?
7)What is compile,recompile and decompile?
8)How do i compile,recompile and decompile?
9)Is it possible to take models from maps?If so,how?
10)How do i make sure the models work?
11)How do i make it spawnable in Gmod?

Hope you answer this questions.