If you want to do back squat (rather than front squat) on lower body day - that is 100% cool. Although I will add - I did a variation on the above lower body work out and added 30kg to my front an back squat in 12 weeks. Front squats for 5-10 reps followed by high rep back squats is my go to. It is some simple and so effective. In fact I stopped doing it a year back and I’m just about to restart that exact work out.
As for you questions:
Depending on your current strength and size yes. I’m fairly strong(ish) and I do a similar amount in my own work outs. Oh add facepulls on the upper body days
It means this:
Press and incline press as both shoulder movements.
As an FYI this programme will not make you pro body builder. But it will help you get a touch bigger given enough time and food.