4) I am not too sure on this , however I was told any summon will follow the registered owner during the saman was issued not the car, meaning any summon unpaid,  the owner will have to be responsible because the saman date will determine who is the ownership of the said vehicle. But usually if you have unpaid outstanding saman, JPJ will block the OT. Just do a simple sale purchase letter to be signed by yourself, seller & a witness on the purchase date just incase this might prove to be useful incase needed.
Usually a runner does this, but if you want to save cost, enquire from JPJ or a Runner [ usually a Runner work for a used car co but some Runner can help you do it and you pay them personally ]