HERE ARE SOME OF THE ANSWERS:

1. Button to summon a servant — We had one in the middle of our dining room when we purchased our house (built 1913). The people we purchased it from, who had had the house built, had live-in servants and that button summoned the maid to the dining room. The hostess could press it with her foot surreptitiously so that no one knew she was summoning the maid. The funny thing though is that when we actually moved into the house, the previous owners had removed the button — but left its fixture and wires. Our house also had two buttons in the pantry that rang bells on the 2nd and 3rd floors to get a servant’s attention and there was a speaking tube next to them so when the cook was in the pantry, she could talk to the maid or chauffeur who was on a different floor.
2. I know everyone is shitting on the idea of a servants bell but what else could it be from back in the day? Oh it’s in the hallway? Yeah, they stuck them everywhere in the old houses. Maybe this one just didn’t get complete torn out  take a screwdriver and look inside
3. If it’s in the floor near a main door I suspect it’s part of a lock/door security. The lock on door would have a rod that connected to the floor, preventing people from kicking it in.
4. We had a servant button in the floor of an old home that my parents had fifty years ago. The home also had a coal chute.
5. Yep, butler call bell, our old family beach home had one under the dining room table!
6. You can see that’s a finger pole so whatever that is it was meant to be pulled out. It may have been quick access to plumbing underneath the floor. It’s been nailed in place you can see.
7. You stick a key in that and it should open up a part of floor. It would have been used to cool the house.
8. Something to make you ask questions. Pull it and find out ! Do not stand lnkt!
9. At first I thought it might have been an electric outlet added in at some point later in the century but now have no clue! Will be interested to hear what the conclusion is on this one!
10. Picture of the whole room might help. I’m guessing a hole for a leg/latch on a removable room divider.
11. It looks like it has three pins in it, which looks like a microphone jack to me, but I can not tell what size it is.
12. A iron rod goes in it if it’s near a door. It’s to wedge in that whole to a similar whole in door. So you can break in. Possably. It looks similar to same I’ve seen in an old house. I believe during g prohibition they were popular.
13. A hatch
14. Wiring, when the electrical came in and gas was removed
15. Most likely a plumbing valve access
16. the floor latch for interior double doors
17. Maybe access to a cut off if a gas or water supply is upstairs
18. If you can’t search it out, get a copy of the floor plans from the city
19. Secret safe
20. Just open it
21. Latch for storage compartment
22. It looks like a pocket door used to be there.
23. I’m going with room /wall divider
24. It’s a floor safe used to hide stuff in there
25. Call button. Probably had a bell in the kitchen.
26. Something to make you ask questions. Pull it and find out ! Do not stand lnkt!