werewolf girl has several types. feral does not do that. also the "scentless" perk exists to help with it. werewolves are there to prevent people from just putting all of their points towards strength, when there is also agility and magic(a bit stronger imo).
Locked up does not require buttplug. just anal addict and chastity cage. Also the merchant is known for the amount of bad endings. a tip is to stay away from the merchant if you have anal addict 3.
If you don;t want to lose your progress, dont play on ironman. Ironman is largely used to get the + versions of achievements and most of those achievements are bad ending in the first place. All of the achievements that were out when you posted this could be achieved at level 1 (except for the patreon story mode : wrong way achievement). The benefits for these achievements are greater valued bonus points to improve stats in the game. high replability.
Merchant is not a recommended end game event, unless you are an anal virgin. Merchant is mostly used to get the achievements that are the bad endings. It almost feels like that was what the merchant was made for.
I just obtained 3 newer achievements in ironman mode in one run that in total required me to be a total virgin while beating the demon king in about 3 hours.- how i saved time was by using the skip button to speed up certain scenes that I know aren;t too important.
Merchant perfect toy check is an achievement so that is good news. The merchant achievements i beileive are the only ones that require any merchant items, except for nursery I think.
There aren't really any unavoidable fails but just regular fails. Like the fails are built in, but the best way to avoid them is to stay away from the causes. It creates scenarios to look out for. try not to be too receptive/a total slut in the game. just getting banged all the time to get through the game is likely not what the creator intended. It is meant to combine all of the traits and try to put them to use.
AlsoI believe there is willpower in the game that is intended for some of these fails in order to not get a game over. i believe characters start out with 5 and they can use them in certain cases where a fail may occur. You can also regain them from doing or undergoing diffficult tasks.