Identifying Old Pool Parts for Repair / Replacement

Pardon the re-post from u/swimmingpools on Reddit, but I’m trying to get as many eyes on this as possible.

Last year we purchased a house from 1966 which included an original swimming pool (gunnite, we think). The pool itself has been neglected over the years by various owners and I feel we just skated by last summer without major incidents. I drained it this past fall so I could start tackling some projects. Namely replacing broken tile, painting the surface, and replacing any missing or broken parts. The latter is the reason for the message.

Could I get some help from some of you on identifying some of the parts in the pics below?

Part #1: https://imgur.com/a/31jIrtJ

This is some sort of vent that we can’t identify. It’s near the expansion joint of the decking but doesn’t line up with it.

Part #2: https://imgur.com/a/IevY5WQ

90% sure that this part of the drainage system. There are a handful of these in the pool, plus one in the spa. The spa is the only one that seems to function in a drain capacity. The rest look like they have been plastered shut (either intentionally or by accident)

Part #3 https://imgur.com/a/BCT8B7g

There are 4 of these evenly spaced across the pool surface. Best guess is that this is meant for a pop-up head/cleaning jet, but I can’t confirm it. All 4 are empty. It could also be that these are just covered/sealed versions of part #2