Some of your questions such as visa requirements are not easy for non-Pakistanis to answer as they are different for each nationality, I am guessing it might be easier for you than a European in muslim countries but you will need visas for the European countries that we do not.
It is possible to do this trip on just about any bike provided it is in good mechanical condition, if you have limited finances something small like a Honda CG125 will be perfectly capable as long as you are not in a hurry. You will require at least a full motorcycle licence, an international driving licence which you will have to get from a local motoring organisation and some medical insurance.
You will probably find it much easier to enter Iran than China with your own vehicle so might want to plan your route starting in that direction.
If it's in the Touratech catalogue then you don't need it
"You've got to think for yourselves! You're all individuals!"-Brian of Nazareth