Hey could someone tell me whether it's a good idea to hold position in mid-squat? And if so what would be the safe duration? Also I read somewhere that when performing a squat the knees should not get past the toes. Is this humanly possible?

They mean don't lean forward! (it'll hurt your back)

I don't know about the position-holding thing, I don't see a point to it

Youtube has multiple videos about squating safely.