The short answer is yes. You can check out the official documentation for more information: https://www.odoo.com/documentation/17.0/administration/maintain/hosting_changes.html#to-on-premise

I hope this helps!

Yes it's possible, this is exactly what I did. I'm going through the migration to OnPrem right now, everything seems to be working but still in the final test phase. The official documentation  https://github.com/odoo/design-themes and add the path to addons when calling the CLI or in your odoo.conf file.

2. By default odoo will listen on 0.0.0.0 in otherwords any incoming IP address, you should have a firewall on your server to block incoming traffic directly to odoo but I recommend adding http_interface = localhost to the conf file. I actually think this default behavior should be changed, but thats a separate topic.

3. I couldn't really find documentation on using he CLI backup/restore functionality the utility itself has documentation, but I actually had to look at the source code to see how to get to the right sub command to get the help needed. If you call odoo-bin db you can get the help info needed for backup/restore.

4. All addon paths must exist or Odoo barf at runtime. If you intend to have a placeholder path for your own custom addons you need to make the directory during your setup process.

5. When testing the migration you'll want to use the -n neutralize flag, this neutralizes EVERYTHING. Even for testing I find it to be a bit overkill. For instance if you want to test stripe in test mode, or easypost, or even just capture emails with something like mailhog or mailpit, you'll need to either do this manually in the test instance, or you can look at the neutralize files in the code base and figure out how to change/customize settings for your test purposes. For instance setting a test domain.