No, you can install and use ISPERP for free
Yes. After you have installed a ISPERP server, you automatically get a 14 days trial period in premium mode.
The server will continue functioning normally with all the basic features. Only premium features will be inactive. Your server license is switched to the free mode.
Yes. You can specify which ones you want to be premium through Settings->License.
No, you do not lose your license. You can simply reinstall ISPERP on a new server, and restore your database from your backup file.