The upgrade path lists both 8.0 and 8.1 as possible interim releases on your way to 8.2
Remeber that with 8.1 python3 is the global default and for some uses you can switch back to python2.7 but not for all. So in general - you _should_ upgrade your apps to python3 ready if upgrading to 8.0 but you _must_ do that if upgrading to 8.1.
Check the Release Notes for each version between 7.x (why the secret version #?) and 8.2. Depending on how low x is interim upgrades may be required.
Reverting to previous Splunk versions is not supported. Make a backup of $SPLUNK_HOME before each upgrade step in case you need to revert, but that may not protect against all changes made during the upgrade. See $SPLUNK_HOME/var/log/splunk/migration.log for the changes made during the upgrade.
Splunk docs are at docs.splunk.com. Release Notes are at https://docs.splunk.com/Documentation/Splunk/8.2.6/ReleaseNotes/MeetSplunk