In the US, I would just call it an 'upper level,' 'second or third level,' or even 'second floor.' Technically, because it is open to a central area, it could be a mezzanine, but we would probably tend to just use simple language like 'level' or 'floor.'

I would call it a mezzanine level

Assuming it is not just a viewing place, but has stores, etc. on it I would just call them "floors" or "levels." There are all kinds of specialized architectural terms, and, as others have mentioned, the word for an incomplete floor is a "mezzanine." But I would never call the structures in your pictures "mezzanines" or "balconies." The big exception would be structures that use that term on interior signage themselves. For example, our local public library has a "mezzanine floor," and the elevator and signage say "1st-Mezz-2nd-3rd"). In the case of a mall, there are usually big store directories with maps and floor plans, and I'd just whatever terms the mall itself uses.