Pillars of the Earth style inventory/clues

You could use animations & force the animation frame numbers based on values. Would need a bunch of if elseif queries too if you only want to use a single button per slot.

I haven't read all of this thread, but Daedalic tend to make their own custom systems comprised of a mix of interfaces, action parts & Lua script - maybe it's not something you are capable of creating yourself currently, but you can always use something simpler until you have acquired the knowledge to create what you originally wanted or find/hire someone else to sort it out for you.

No, you need Lua script.

That's how you would force a playing animation named animation_name to loop the first frame only.

Also, I never said "give up", I said that you can always work on other things in the meantime & come back to it later on. Diving ass first into the deep end is not always the best approach; well, more often than not...