1. It's complicated to do and the Tails developers are against it. Do you want to run Tor over a VPN to hide your Tor use from a local observer? In that case you can use bridges. If you want to run a VPN over Tor to get a non-exit IP address, there are lists of web proxies you can use, like http://www.publicproxyservers.com 2. Tails has a MAC changer called macchanger. It doesn't run at boot though.