1) Not all beta applications are accepted. The AG team is likely looking for those users who have a GitHub account and can actively test betas and report issues to the GitHub issue tracker(s), and not those users just looking for a free license (which unfortunately there's likely a lot of those type of potential users, which the application process likely helps weed out).
2) There's no immediate response - usually there's a backlog of beta tester applications for the AG team to go through, so a response might take some time (e.g. a week or so). If you don't ever receive a response (like after a month), then the application was likely rejected.
3) You don't actually need a beta license to test the beta versions of AG. Just switch the update channel to beta and start testing.
Here's a good recent topic that might be a good read.