Due to how flexible and configurable DNN is, there isn't always a clear path that works the same for every DNN website. Depending on the custom modules and other extensions you might have, you may find yourself taking different steps from another site that appears to be the same.
In general, the steps I'm suggesting are covered in the following resources:
The path I see for you with the details provided are:
- Upgrade/load a new development environment for your custom extensions using DNN Platform 9.2.2. Rebuild your custom extensions and make any necessary API updates (warnings and errors). Increase their versions and have that build ready for later.
- Identify all third-party extensions and find their latest installation packages. You may need to pay for an upgrade (it's always worth it). Have these packages ready.
- Clear out your Install folders.
- Back up the website and database now, and again after every upgrade step.
- If necessary/possible, upgrade all possible third-party/custom extensions.
- Upgrade DNN to 09.08.xx.
- Repeat backups and extension installs, as necessary.
- Upgrade DNN to 09.02.02.
- Repeat backups and extension installs, as necessary.
- Upgrade DNN to 09.09.01.
- Repeat backups and extension installs, as necessary.
- Upgrade DNN to 9.10.02.
- Repeat backups and extension installs, as necessary.
- (Optional) Upgrade DNN to 09.11.00 (but I'd wait for 09.11.01).
- (Optional) Repeat backups and extension installs, as necessary.
Follow the typical upgrade process for each version, but as you test this locally, be sure to note which versions you find you need to upgrade which extensions. Usually, you upgrade the extensions at the soonest possible version prior to upgrading DNN. So, you may find you need to upgrade many of them right away. Others might have to wait until after DNN 9.2 or 9.6 (or another version).