Yes, it will expire one year from the purchase date.
Yes.
If you save your "master.lic" file, you can re-install on the same computer without having to contact anyone.
The $299 version never expires, but, you will only be able to use the updates for that year...so, if the last update is something like v17g, that will be the newest version you could use.
As I've said, the $299 version doesn't expire.
Current models are generally backward compatible to all versions until v13 (except for things that don't exist in the older version)...the files changed in that version. However, all older files are still useable in the current version.
Hope that helps.