1) Used the El Capitan just fine, after my airport is sold, I had to connect, to my old router, many problems. I moved into new house new router I can't even connect. I tried many things, the WiFi tries and tries to get connected but without anything happen. 2) I want to downgrade right now, I have also an iMac if that helps. I haven't kept any backups. How should I do the downgrade?