You can only sell Full Rights once, so once you sell it you can't sell it anymore. If you want to sell it more than once you can sell it for Learning Rights.
Learning or Wearing rights. There are only certain signatures that can be sold multiple times for full rights such as Pegasus sigs, etc. Good luck selling, Snipe.
Yeah its probably those special sigs like I said above, those signatures were made before the rule went into place so they were made as an exception. As for whether it is pro or not... I would say its Moderate or Intermediate. Snipe.