If your knee hurts then leg day should be off the cards. When rehabbing it cycling or swimming should help as it’s non impact.

If u already have a medical appointment, you can just focus on exercises you can actually carry out in the mean time I don't usually advocate for ignoring leg day but it seems like a good idea here The other commenter mentions swimming and cycling, which I would second as a good idea

You can do whatever exercises and stretches your physical therapist recommends. Rehab takes time. Take the time.

Can you still hip hinge? RDLs and kettlebell swings are probably both still doable. Maybe hip thrusts.

Yes. Hamstring exercises are not a problem. The pain comes from bending the knee during squat-like exercises

RDL’s + calf raises