Silver 5-Tier Boltless Steel Garage Storage Shelving (48 in. W x 72 in. H x 18 in. D)

If you mean to only make it half as tall with 3 shelves, yes. It's very stable with 5 shelves and full height of 6 feet. I'm not sure how stable it would be at full height with only 3 shelves. I wouldn't risk it with a heavy load.

Yes, I put mine together in a corner, you would only be facing one extra wall and the doorway choke point. In your case, just be careful you have enough height, as you’re gonna have to tilt the shelf faces themselves to get them in. If the doorway chokepoint is severely smaller than the shelf itself, I would expect trouble.

I no longer have the packaging. The packaging was inadequate in that there was damage that the manufacturer quickly resolved after I called the mfg number inside the box. Package size is somewhat larger than the 4 shelves which are the biggest pieces. Shelving went together easily once I had all the pieces. If you can ship to store and pick up there, do that. The carrier noted to delivery folks that the box was to be handled by two people. Heavy. Hard to handle. Not sure of your vehicle.

I called the manufacture and sent them pictures of the bowing. They sent me bar that go across the shelf in the middle. It seems to be holding the weight, at least for now. The bar also helps hold the front and back brace from separating allowing the board to fall.

Hi John, unfortunately it is not offered. We apologize for the inconvenience. We appreciate your business and look forward to serving you in the future. Thank you for shopping Home Depot!

It has been in my garage, all set up and doing it’s job. Stable and easy to set up.

Approximately 26" X 75" X 4"

No. You'd have to buy or build a dolly for it to sit on.

I seriously doubt wheels can be added. Its a nice little shelving unit but the angle iron used for the frame is pretty thin and it would be difficult to mount casters or whatever wheels you were thinking of.

It's 5 feet tall. So you could technically use the brackets from a second unit to add another 2.5 feet (half of the second unit). But I wouldn't advise it unless you were securing it to a wall, because it's narrow (at only 12" deep), so making it that tall could be a tip over risk.