A beat license gives you the rights to record with the respective instrumental and to release this commercially. Depending on the license, there are different limits, which I have deliberately kept simple.
No, you only buy a license to use and publish your song with the respective beat. This means that the producer always keeps the rights to the beat and can sell multiple licenses for it.
No, these are just a kind of preview to write or pre record. For any publication you need a license. But if you are in my newsletter, you still get free beats including licenses.
In my case, this means that you get each track of the beat as a single .wav file. This is especially important when mixing your song to be able to edit certain elements individually, for example with an EQ to get space for your voice.