I have a MacBook Air 2011 with 4 GB of RAM. I installed Yosemite, and I have two problems which I cannot resolve: 1) The Juniper Networks client software that I need for VPN access is incompatible with Yosemite. When I disconnect, I lose Internet connectivity until I reboot. And if very often disconnects all by itself. 2) No driver for my Samsung ML-D2850 laser printer. I want to restore back to Mavericks. I have made Time Machine backups, but I'm not sure if that's the way to do it. How can I go back to Mavericks? Thanks!