They might lend you a key to block the elevator so you don't have to contend with the door closing all the time. In any case, it's better to plan to make more trips than to try and pack the elevator. You can fit a big load on a dolly if you work at stacking stuff onto it gradually, not in a rush. You might be responsible for vacuuming up the drywall specks that fall off.

Sounds questionable. Variations from 2 to 3 inches are rare. Chances are you don't have them, but even if you did, putting down parquet wouldn't disguise them. Get a long straight board and/or a level and set it on sections of the floor. Making a blanket statement about all concrete floors being out of level is inaccurate. The parquet in the unit was probably done because it was an inexpensive wood floor, not to deal with a subfloor issue. Floating floors are very sensitive to level however. They generally use the same specification as architects which is level to 1/8" within 10'. Humps in the floor can cause areas to be bouncy. This is generally easily fixed by doing some floating.

Thank you for the suggestion gardengal48, I like the idea of a conifer too! I can look into some options. I've done some more homework on dogwoods and definitely doubt that will work. Still keeping fingers crossed for a dwarf river birch too though! To answer some additional questions, I'm in Jersey City Heights about a mile in from the Hudson River. I'd like to leave the pots outside in the winter, but perhaps wrapped in burlap if need be. The balcony is 10' by 4' with railings just shy of 4' tall, I'd make sure any potentially taller plants were in short, heavy planters. Thank you for the guidance!

You might be able to put the compressor unit on the balcony, and then feed refrigerant to a unit on the inside wall abutting the balcony. Let it cool everything, or else you have to pay for more expander heads and the plumbing. Also the heads have to drain, and I will be happy to regale you with possible issues associated with doing so. A few years ago (in NH) I had installed two Mitsubishi systems, one 4-head and one 2-head. Four of these heads are on interior walls. I think the price was near $20k to cool 2600 sq. ft. If you are only supplementing the building AC in the summer, and doing moderate cooling in the fall, you may not need a very powerful unit. I can say that the compressors and the heads are very quiet. You can hear the fan at the outdoor compressor. It is about as loud as a window fan on low. At one point one compressor developed an intermittent racket, fixed by some adjustment, when the compressor iced up trying to pull heat from near freezing humid air. They are designed to de-ice, but I think between fan alignment and ice build-up there was a bit of overlap that needed to be adjusted. You will need a hole in the wall to contain two refrigerant lines and a control power line. The lines to the compressor unit will be covered by a plastic cover. You will need an outdoor disconnect switch and power feed of 20 to 40 amperes at 240 Vac. Your balcony may be subject to a warm air breeze from the compressor unit, depending how it is placed.