Laying the floor before plastering is actually not possible. Plasterers generally work rather roughly. They are no virtuosos.
I guess a plastering machine is used for large surfaces. Have you ever looked at what kind of hoses and pressures are used there? Probably not. Even tracing paper is not enough to cover it.
The hose couplings alone, so-called banjo couplings, are made of solid metal, heavy and angular with 2 protruding safety locks. If one of those rubs over your floor once, it’s ruined. If a hose should burst, which can always happen, you’ll have a huge mess.
So I would never do such nonsense. Ladders or small scaffolds also scrape on the floor. Add to that the moisture. The plasterer will curse you or even raise the price because he has to work slowly.
So a definite no. You cannot lay the floor before plastering.
Regarding the other plastering work. I don’t think much of gypsum plaster in a solid house. It’s nice for the plasterer to work with and also to get smooth walls. Still, I would always prefer a lime cement plaster. Gypsum plaster attracts moisture and odors. I only use it in emergencies.