My plates are extremely faded almost not visible.. Am I allowed to use a vintage plate until new updated ones are issed? (Heard discontinuing wave plates) obvi transfer reg sticker.

If you put in for new plates ( replacements ) I would just wait for the new ones. You'll need to turn in the faded ones when you pick up the new ones

You can ONLY use the plates and registration that are assigned to that car, if you have other plates that are still active then you can transfer from one vehicle to the other but you have to close your current REGISTRATION and turn the plates then fill out the proper paperwork for transfer from one vehicle to the other but the other vehicle will be unregistered and that's all providing both vehicles are in your name