Yes, you can upgrade into the inactive partition and do the switch-version at a later
time. You will need to track any changes that are made to the db between the upgrade time
and the switch-version to redo them after the final step
The 8.x Software feature license will be added after the switch-version is completed.
All node and DLU licenses will be migrated during the upgrade.
The upgrade from 6.1(4) to 8.0(3) is a direct upgrade path as shown;
Check out Table 8:
"Show a little faith, there's magic in the night" - Springsteen