Well, it may be atrophied a bit from lack of use and the skin might be a bit flaky. Physical therapy can be painful, not terrible pain, more of discomfort, but it is necessary to fully rehab after an injury. I have had broken many bones over my lifetime and have had more than 1 cast.
your arm will be fine after your cast comes off. it will look lighter in color from wearing it. as for the physio....it will have some cramping, but after it loosens up, your arm/hand will feel better and regain full use of it. :)
sounds like you have had your fair share of accidents and injuries. you must be athletic, or just clumsy. lol. hopefully athletic :)
Your skin will be scaly and if you are doing it right, physio will hurt.