Regarding your questions:
1. You can use Boxcryptor with a local account - in this case, all data is stored in a key file on your computer and no connection to our servers is required. And yes, a local account can also be upgraded to Unlimited Personal or Business in order to use filename encryption.
2. You can only have one Boxcryptor drive and being logged in with one account at a time. Within the Boxcryptor drive you can define various different locations (what would be multiple volumes in BC Classic).
3. Easiest way would be to have both applications running and simply copy the files from the Boxcryptor Classic drive to the Boxcryptor drive.
4. Boxcryptor auto-detects removable drives and automatically adds them as a location in the Boxcryptor drive.
5. Boxcryptor Classic has simply reached it's "end of life". With the release of Boxcryptor 2.0 ~2 years ago, we decided to focus our efforts on Boxcryptor 2.0 and keep our 1.x versions available as Boxcryptor Classic. We also announced that we would support Boxcryptor Classic to keep it up and running but we would not add any new features (like support for new operating systems).