I’m sorry I can’t be of much help, but here’s what I know/remember.
Exe Create games usually don’t contain complex puzzles. You shouldn’t encounter anything harder than activating a switch here or there.
I don’t know the details concerning ACP (3DS) or don’t remember them (Steam), but I still know that the game was rather stingy in this regard compared to other games, so spend your points wisely and/or prepare yourself to grind a lot. By the way, I would be surprised if there was a way to earn more ACP by paying real money in the 3DS version – none of the Exe Create games on Steam offer such a method (the Smartphone versions are a different topic, of course). At least you can try to see if obtaining two Weed Supplements increases the ACP output:
https://www.rpginsanity.com/forum/asdivine-cross/39705-weed-supplement-and-its-purpose/
Unfortunately, that was the only thing I missed during my playthrough, so I can’t even say if it works in the Steam version.
Concerning the weapon fusion system, you can transfer, strengthen and add effects (everything portrayed as a symbol), but you can’t transfer the effects of the weapons themselves. If, for example, a weapon effect (description) says “increases strength by 50%”, this effect can’t be transferred to another weapon.
Finally, a “warning”: Asdivine Cross is one of the few Exe Create games (and the only one among the ones published on Steam) where you need a full second playthrough in order to obtain the true ending. Despite hating this kind of game design, I had a lot of fun playing the game, but it’s good to know what you’re getting yourself into beforehand.
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