Things which render the Salaah Makrooh

Pants below the ankles

Q:

1) If you pull up your pants to ensure that it remains above your ankles before going down for rukhu or sajda, does it break your salaat?

2) If your pants falls below your ankles while reading salaat, does it break your salaat?

3) If you perform salaat with your pants below the ankles, is your salaat valid?

4) what type of movements nullify salaat?