Are you sure it’s not possible to do so in one playthrough? As far as I can see in the game’s startup file there is nothing out of ordinary. It has tracked variables for:
- Each item of clothes you own. These variables are used to unlock corresponding options during the choice “what to wear for the concert”.
- How many items of the same type you have. For example, each time you unlock a coat or a jacket, it gives +1 to the variable totaljackets. I presume that once this variable hits 6, you are granted the achievement “Jacket Enthusiat: Collect six coats and jackets”. The same thing for collecting 4 hats, 3 wigs, 6 dresses/gowns. And for having a caftan and a cape simultaneously.
I don’t have this game, so I can’t check the chapters where these achievements are granted, but from the startup file they are based on regular variables. I doubt that the trick is in the redirecting to the new game from epilogues file, otherwise it would be possible to get the achievement for 6 dresses choosing exactly same dress in the first chapter for 6 playthroughs. Or it would require many additional ifs in the scene where the last (chronologically) piece of clothes is supposed to be obtained: to check if the counting variable is >=4 or 6 and to check if other items of the required set are actually obtained.