I've encountered a serious, possibly game-ending, bug with the backpack. First, when you have bought it and are in the wardrobe at home, there is no way to assign an outfit to the backpack. In the Clothes tab, Pick Outfit gives the yes/no prompt to select outfit, and choosing yes gives the instruction to click on an outfit. But no matter which outfit you pick and whether you click once or twice on it, if you later click on the backpack in a bathroom it says it's changing outfit, but then reports the backpack is empty. At least it leaves you in what you were just wearing.
But wait, there's more! Not only does the assigning thing not work, but simply owning the backpack breaks the functionality of the Clothes tab in the Wardrobe. The only outfits I can choose are the night robe, the maid costume, and the gym wear. I can't put on anything else, because game just ignores any other choices. (This only happens in Clothes - everything works fine in Shoes, etc.) The only way to change to other outfits is in the Quick Change section of Wardrobe. So if you haven't yet saved it in one of the QC Outfits, you'll never be able to wear it.
This is with the Win 5-21 version, but the exact same thing occurred in the 1-9-alpha on a different save file & run. Both downloaded here at itch. These runs were both from the very start, not skipping ahead to change or Alex Corp.
It's especially annoying since the game keeps nagging you to buy the backpack, and then immediately breaks when you do.
Thanks. Have enjoyed this game over the years quite a bit.