what is the command to check if Irule is used in any other VIP ?

Simple would be to extract your config (bigip.conf) and serach from there, or on TMOS try this.

list ltm virtual | grep -B 15 "prdlam-redirect-v1.2"

you might have to tweak your values for -B depending on how much your VS config has.

Try this ->

list ltm virtual one-line | grep ""