Customizing rules, what can and cannot be done

[Alduin Starborn]

I would like to modify a ruleset (let's say pathfinder) to add my custom rules, but before I spend hours delving into the various tutorials (and start learning LUA) I would like to know if the following is possible:

1) Adding spells, feats etc.?
2) Adding a new ability score and change existing rules to make use of it?
3) Modify an adventure module bought from the store (including updating it from PF1 to PF2)?

Thank you in advance.

[Varsuuk]

#1 is easy and no LUA coding is needed (other than perhaps encoding effects strings) - you can enter spells and feats from the UI (an expert can correct/expand if needed.)
#2 More complex but yes, every ruleset defines its own ability scores etc so this is definitely doable but much more involved (and Lua/xml) than #1
#3 This can be done within the campaign you create with caveats - modifying it WITHIN the same Ruleset - your changes can be exported out to be saved (please verify, I don't run games) but you need to be careful when the module is updated. It may require you to "revert to original" and lose your changes (that's why would look into creating module holding your changes in case that is a. possible b. could integrate with updated mod automatically)
#3 Changing rulesets - not familiar with differences in PF - assume they have a common ruleset - whether can load one in the other a PF guy can tell you. No clue if changes are gamebreaking and therefore not allowed to load PF1 from PF2 (doubt other way) but as for changing the modules, bought modules go in the "vault" and are encrypted so you cannot modify them except from FGU/C GUI.

[damned]

You can use Universal Modules extension to load a module in a different ruleset - Story and Maps will work. Other things... will vary but NPCs will almost certainly need to be replaced.