ᐅ Various Caulking Scenarios for Baseboards and Windows

Hello everyone,

Unfortunately, our developer has filed for bankruptcy, so the house was not handed over ready to move in.
I have several holes and gaps in the walls and floors that I still need to fill. However, I am a complete beginner in this area.
I would appreciate any feedback on the individual pictures.

Picture 1: Irregularities near the baseboard. Should these be sanded down and the holes filled? What product should be used here? Can smaller imperfections be left as they are since they will be behind the baseboard?

Picture 2: Floor-to-ceiling windows: Can the black membrane be covered with filler before the floor is installed? Should the corner be extended with filler? What product is suitable here?

Picture 3: Gap under the window. Should this gap simply be filled? Which product can be used?

Picture 4: Holes in the floor. Can the flooring simply be laid over them, or should they be filled first? With what product?

Picture 5: Joints. Which product is recommended for the transition between floor and wall, and for the joints within the wall itself?

Which tools would you recommend?

Thank you very much.
Alex