Regarding your question #2: You the author cannot choose how your music is to be used. When you sell on AJ the buyer can do anything that’s allowed in the license terms. So you need to put a price for each type of license.
Regarding your question #3: No, you don’t get royalties from Envato. You will get a one-time payment at the moment of the sale. How much you’ll get depends on your exclusivity status and the total amount you’ve already sold.
its the license usage, for low views usage is the first price, then the views and licences change, so starting from something small obviously and then going to something bigger, and if you see there is a recommended final purchase price if you are unsure. but you do whatever you want nowdays. so you set the prices
Most internet uses: Music Standard license
Video Games, DVD, anything with physical or downloadable copies (over 10 000): Music Mass Reproduction
Local TV: Music Broadcast 1 Million license
Regional TV: Music Broadcast 10 Million license
National TV: Music Broadcast and Film