Not being able to type one specific word with autocorrect off is such a weird outlier that, with all due respect, I'm not sure if I'm to take your complaint seriously. And for it to be what has to be a top 50 most used word is befuddling. So if I were to try to earnestly help, I'd say:

1. actually double check that you have autocorrect off. Not that autocorrect would or should make "and" impossible to type (autocorrect is on for me, and "and" types just fine), but making sure it's off or at least toggling it on then off again could have an effect.
2. has someone played a prank on you? Settings>General>Keyboard>Text Replacement. Has someone put an entry to replace "and" with "band" or something similar?
3. software really doesn't exhibit bugs unique to you in the way, say, hardware that's been dropped may exhibit unique behavior. If 1 or 2 above doesn't address it, my best guess is you are being disingenuous in your complaint which is why my comments read as dismissive.