I think you can name the file anyhow you like - then go to Maintenance / Subscription page, click "Insert license file" and browse for that file (or copy&paste the full path directly). By default, the "open window" has the .avastlic extension selected, but you can change it to any file.
The file, when accepted, is copied into avast! data folder, so you don't have to keep the copy there anymore.
Yes, 396 is the latest version.