No they did not give me anythingGoogle in that email should have given you an exact reason as to why it was not approved.
Yes, Google requires your website to be at least 6 months old.
What I used to do in the past (I sold Google Adsense accounts) and I'm pretty sure it still works: Make a blogger/blogspot blog. Add some content, apply for Adsense and that's how you get approved.
Yes, Google requires your website to be at least 6 months old.