The knob should just pull off, but sometimes they require full chooch. If she breaks it, it’s not a big deal. If Habitat Re-Store is a thing near her they usually have a shelf of these knobs for almost nothing. If not the big box stores sell them too, and the lights can be turned on and off without the knob until she can get a replacement.

Back when I worked as a handyman I used the old knobs for many things. Some people get very weird about change. I’d usually ask if they wanted the new one to wedge into their junk drawer, though.

They are typical as low-point drains and manifold drains, both on the main line (always charged). Don’t just cap it if that would make a dead end, especially if it’s sloped down to drain. I can’t tell very well from the picture, but if it’s on a tee you would be okay putting in a threaded cap.

“king drains” or auto drains are common. A short nipple and either a brass cross-top or pvc ball valve would be better. Just be sure that it is accessible in the end.

Hollow doors have about a 1" frame of solid wood around the perimeter.

If the door frame is not currently falling out of the opening there’s enough meat in the opening to mount a new one. Fondots is right. Re mortising well for the hinges and modifying the door to fit will be more effort than getting a pre-hung.

Picture looks like real wood and not paper, hardie or vinyl. Venat0r has the right idea of taking a sample in to your local yard. A couple possibilities I came across online are https://www.becn.com/products/siding/wood-siding/C-503734 and https://truwoodsiding.com/products/1-2-cedar-shake-lap-siding/ although the online pictures are garbage for them.

Heavy on the “peer”, light on the “review”

You’re one of today’s lucky 10,000

When I make them I do bisquick biscuits with a handful of shredded cheddar. A little melted butter and italian seasoning tops it off.