Yes mate do squats first.
squats =legs general
leg press=quads,buttocks,secondary hams
leg extensions=isolation quads
reverse curl=isolation hams
Lift heavy on the first 2 compounds,and do the isolation after. if you like in the leg extension in every rep on the top, make a full stop legs extented count 1001,1002,1003 and then go slowly the negative. Incredible burns,welcome to hell