Glad you like it. As I said, the custodian mode is unfinished but should give you a taste of what's to come. There will be exclusive cutscenes and other story moments. The intention is to make playing through that mode different depending on "when" or "if" you use the item.
As for the special item, it only stops you aging for now, but I'm currently working on the main character sprite rework. Once that's done, using the infusion will slowly alter your appearance. The generals and other people will recognize who you really are and will act on it.
All of that is not finished yet and will take some time to add, since there are way more pressing things I need to work on.
Also, last age sprite is for age 17. Full game will end once you reach age 18 (Game ending after the first year right now is only temporary), so there is no need for more sprites. I MIGHT make more sprites for the post game, like one for reaching age 30 or 60, but I don't think that is necessary right now.