For the tutorial 12, i'm not sure but i think the required file is missing as you also noticed, so that tutorial is broken unless you recreate the missing files, but then there is no need to make the tutorial if you are able to fix it
Check the wiki, it has some infos, maybe there is a solution to this problem there.
The only difference between a side quest and the main quest is the way you update the steps in the quest journal, there are secondary quests update actions, and primary quest update actions, but for the rest of the actions, both types can use them.
So yes, you can use Illuminate X as Primary for both a main and secondary quest.