It’s amazing how often that’s the solution.

Once upon a time well before I was born my dad was a pipefitter, he still had most of his tools and so growing up we were sort of the first-line troubleshooters for everyone in my family when they had a plumbing issue. He had a pretty impressive collection of absurdly-large screwdrivers that you’d look at and go “when the hell would you ever need this?”

Until you came across a giant screw like this, or you had the tank off a toilet and needed a 2ft long screwdriver to reach the tank bolts properly.

When you say it won’t loosen when turned, do you mean it’s totally seized up or it spins but the part doesn’t come off?

If it’s totally seized up, have you tried dousing it with some sort of penetrating oil? WD40 might do it a pinch, but a specialized penetrant like PB blaster or liquid wrench would probably be better.

Soaking it with some CLR or something might also help to break up and rust, lime, or other crud that might be in there.

Still won’t come loose? Get the beefiest screwdriver you can find that will fit the slot. Maybe give it a couple good love taps with a hammer and see if that helps bust it loose.

If you can find a suitable bit, an impact driver/wrench may do the trick too.

Get a big ol’ set of channel locks, vise grips, a pipe wrench, etc. that you can grab onto the screwdriver with to give you some extra leverage, and go to town.

Sometimes a little heat will do the trick, you can try hot tap water, boiling water, heat gun, and blowtorch if you’re willing to accept a bit of a risk.

If it’s spinning but you don’t seem to be making any progress

Do you have access to the back of the tub? Often there’s an access panel so you can get at the plumbing. If all else fails you can try to take the drain apart from the back/underneath

EDIT: I suspect this is part of a pop up stopper something like this- https://youtu.be/c5_o166BCDQ (not my video) just so you have some idea how this thing goes together

Edit 2: sorry I fired off a couple quick thought and this is still rolling around in the back of my head because I’m havi a slow night at work. These pop up drain stoppers are like $15. Don’t worry about breaking them too much, the whole assembly pretty much unscrews. Bust off the plastic parts and if you need to cut off the screw head, get a tub drain removal tool (also about $10 -15) try to find one that’s hollow if there’s still some screw sticking up, unscrew the whole drain and replace it.

There’s a few ways you can tackle this with various degrees of rightness.

First of all, your door looks to be hung upside down. That’s not going to affect the fit of the door but it is going to put your doorknob at an awkward height.

Your best bet is probably going to be to go get a new, pre-hung door, and replace the entire thing, frame and all. It’s really not that hard, just kind of fiddly getting everything squared up properly. You can probably get it done for less than $200, and a few hours of work with a friend or two.

Second best bet is going to be to square up the existing frame, get yourself some shims a prybar, and some nails, pull off all the trim, and set it right.

In my experience, trying to get a new door to fit right in an existing frame is always kind of a pain in the ass. It sounds like more work, but it’s usually worth it to go the pre-hung route.

There’s lots of guides and YouTube videos on how to do all of that.

Least right- start modifying the door and/or frame so they fit. Cut, plane, chisel, and/or sand the door and frame down until they fit. Yes, the door is probably hollow, but you should still have probably about an inch or so of solid framing around the perimeter of it to work with. There’s a good chance if you go this route you’re going to find it looks kind of wonky and you’re going to wish you did one of the above options.

You could always of course pay someone to do it the right way. Shouldn’t be terribly expensive, I’m a cheapskate and will DIY most things, but I have a personal dislike of installing doors, so it’s something I’d be willing to pay for.

Depending on how you can rearrange furniture, how much wall space you have next to the door, etc. you could also go with barn doors and just bypass the crooked frame entirely. I hat barn doors, I think they just look bad in pretty much all cases, but they’re popular for some reason and pretty straightforward to install.

Depending on your tastes and how much of an actual barrier you need, may also be able to get away with bifold doors, a curtain, cafe/batwing/saloon doors.