Windows above 72 inches from exterior grade are required to have a sill at least 24 inches off the floor to meet 2012 IRC requirements, which should be what you're required to comply with (IRC at least, it might not be 2012 but AFAIK it's been 24 inches for years). If you can limit the windows from opening more than 4 inches, or use a "Window Opening Control Device" that limits it to 4 inches, but releases with more pressure (no more than 15 pounds, however), then they are OK below the 24 inches. Here is a link to the code.
If you prevent the bottom sash from opening at all, and the top of the bottom sash is no less than 24 inches from the floor, then it meets the requirement. Your closet window needs to meet this requirement as well (meaning, allowing it to open freely from two inches above the floor is not OK). Or, you can install guards (I'm guessing that the guards would have to prevent a 4" sphere from passing as well).
Recommendations from my own experience would be to replace the glass with tempered if you are able (I'm surprised it's not required), just in case a window breaks there will be less of a chance to get cut. And, if you're expecting to have rambunctious kids (or dogs or whatever) in the house, I would install guards even if the windows don't open. Just in case.
TL;DR -- find the breaker that shuts that red wire off, then slap the builder with it, so to speak
The builder of your house needs a slap with the NEC. There are two very clear Code violations here, and they're both things that are trivial to avoid.
First off, the lack of panel labeling isn't just a massive inconvenience to you, it's against Code -- the NEC requires it so that the next electrician/homeowner who looks at the panel can actually figure out what breaker to shut off to make a circuit safe or get that sparking oven to quit. In particular, it'd get dinged for busting 110.22(A):
110.22 Identification of Disconnecting Means.
(A) General. Each disconnecting means shall be legibly
marked to indicate its purpose unless located and arranged
so the purpose is evident. The marking shall be of sufficient
durability to withstand the environment involved.
and 408.4(A)
408.4 Field Identification Required.
(A) Circuit Directory or Circuit Identification. Every
circuit and circuit modification shall be legibly identified as
to its clear, evident, and specific purpose or use. The identification shall include an approved degree of detail that
allows each circuit to be distinguished from all others.
Spare positions that contain unused overcurrent devices or
switches shall be described accordingly. The identification
shall be included in a circuit directory that is located on the
face or inside of the panel door in the case of a panelboard
and at each switch or circuit breaker in a switchboard or
switchgear. No circuit shall be described in a manner that
depends on transient conditions of occupancy.
Second, what you have is indeed a Multi-Wire Branch Circuit (MWBC) -- the 52V on the black wire with breaker #23 OFF is stray capacitive coupling from the still-live red wire. The red wire, of course, is still live because of another Code violation, this time of 210.4(B):
(B) Disconnecting Means. Each multiwire branch circuit
shall be provided with a means that will simultaneously
disconnect all ungrounded conductors at the point where
the branch circuit originates.
So, it's time to find the breaker that turns off that darn red wire (leave #23 off while you do this!). Hopefully it will be adjacent to Breaker #23 -- in that case, you can get a handle-tie from the electrical supply house and handle-tie the two dodgy breakers together to fix the issue as per 240.15(B)(1). If the builder was as clueless as I fear though, that breaker is somewhere totally else in the panel -- something you'll want an electrician to fix.
Best Answer
In the cases where I've run I to something like this, the hotel originally had open walkways around the rooms -- allowing more light in, and probably cheaper to build -- which were later closed off with an outside wall to provide a sheltered approach to the rooms and to reduce energy needed to heat or cool the rooms. The windows were left in place because there was no pressing reason to pay the cost of redoing that wall.
I can't vouch for that having been true in this case, not having seen it and not knowing the building's history, but it seems more likely than a local code weirdity.
Remember, most hotel staff turns over fairly rapidly, up to and including managers. Odds of anyone actually remembering the reasons for anything done a decade ago are low... but odds of their admitting they don't know aren't much better.