It is not always possible to upgrade multiple versions in one step. When this is not the case, if you attempt to skip a critical release you will see this message when trying to update the database schema:
You must download and upgrade successfully to the specified version. This is the list of versions that block upgrading:
You should review the general installation instructions to check for any changes to minimum version (eg: minimum PHP version) and other requirements.
Backup Your Database
While upgrading is usually a fairly straightforward process, from time to time fairly significant database changes are made. Efforts are made to make these changes transparent, but as a precaution you should create a backup of your database prior to upgrading in case you need to revert the upgrade.