2 questions, since I have a H9 Max, I just have to buy a H9 Core register it to my account and it's automatically upgraded to a Max? obviously I cannot sell as a Max but am I correct here?
Yes, you are correct.
Also I would like to be able to use an expression pedal but do not want to spend too much, this Max purchase was intended else where but when I realised what I can do am looking @ a 2nd
We have an FAQ with a list of expression pedals that are known to work fine with the H9. You could check the prices on some of the pedals mentioned there and choose one that suits your budget.