Making the basement usable - insulation

Hello everyone,

I am currently a bit clueless about renovating a basement room. The house from 1985 is fully basemented and there is a room with a window (~ 1 sqm) and a radiator. Until now, tongue and groove panels were screwed onto cross battens and the exterior walls were "insulated" with Styrofoam (~ 2 cm) behind the panels. Now I don’t find the wood look so incredibly beautiful and want to reclad accordingly. I have removed the wood panels and cross battens and concrete appeared. Now I have the following idea but don’t know if it all works/is sensible. The room is to be used as an office/guest room.

A. Exterior walls
I wanted to stick climate boards to the wall (according to the respective specification) and cover them with roll-on and brush-on plaster (diffusion-capable). They should on the one hand insulate, but also be able to absorb and release moisture and ideally also look good. Is that well possible for a layperson?

B. Interior walls
For now, I simply wanted to prime and also apply roll-on and brush-on plaster here. If I still want to put up some boards here, what would be suitable? Climate boards are relatively expensive, so I don’t necessarily want to line every wall with them.

C. Ceiling
On the upper floor above the basement room, there is underfloor heating installed. Does it make sense to insulate the ceiling of the basement room?

D. Floor
What kind of floor – suitable for laypeople – is recommended for an inhabited basement room?

The sockets and power cables then simply lie on the bare wall. I have often seen recesses for the climate boards for the sockets. Not for the power cables... can I simply glue two rows of the climate boards at an appropriate distance so that the cable runs between them?

It would be great if someone could say whether this could work/is sensible... I am really quite inexperienced here...

Best regards

Hello :-) I am not familiar with climate boards, but we insulated from the inside, plastered and then painted. For the interior walls, we insulated to some extent because of the thermal bridges. Otherwise, we primed, plastered, and painted the concrete wall. The electrical wiring was surface mounted (in those rectangular cable "containers", whose name I don’t remember right now), as were the sockets. I would avoid a gap between the interior insulation because of the thermal bridges. We have tiles and design flooring suitable for wet rooms as floor coverings. Are you planning any subsidies? Because ceiling insulation and removing the radiators in the basement could then be an option.