Can you add multiple RF links to one arduino?

can you have more than one radio reciever on one arduino?

can you tune each transmitter/reciever to a specific frequency?

what product can do that?

The problem with using multiple receivers is that they are going to be operating very close to each other in frequency. So you have to look closely at the adjacent channel performance of the receiver. Most cheap receivers have very poor performance in this area so it is likely there will be interference from the other close transmitters.