Hot tub area

If you are not moving the hot tub I would recommend tiling around the tub once fitted as you can not be sure the tiles will crack with the weight of the tub

You can put the tub on tiles but everything has to be constructed well from the sub base bellow all the way through to top of tile. if there is any sign of rock in a tile as the hot tub feels up chances are there crack which also leads to possible punctuation in your hot tub and alternative root could be build a sub base for the tub either mitre your tiles up to rather then underneath (harder option) or you could put tub on sub base and put some sort of timber shell round it or something similar which gives you many options how to get the perfect result as to the tiles round the tub

if the concrete layer is level, it is not a problem for the tiles, but if it is not leveled, you can use a material that levels it so that everything becomes perfect and does not allow the tiles to be damaged, if you need help to make the tiles, contact me and I will give you a reasonable price, thank you

Your only and only best option is level your floor to perfection and then lay tiles. That’s that

to put ceramics in the bathroom, it is necessary to put a layer of concrete

You can install the tile directly on the concrete. You can install a CBU or cement board on the concrete, then the tile on top of that. Finally, you can use an uncoupling membrane between the tile and the concrete.

To reduce the possibility of cracking, an intervening material called an uncoupling membrane can be used. An uncoupling membrane disconnects tile from its concrete subfloor and prevents cracking in the slab from being transmitted upward to the tile job. Available under the brand names Schluter Ditra or Redgard Uncoupling Mat, this product is also known as anti-fracture membrane, crack isolation membrane, or crack suppression membrane.

Assuming the concrete pad has been levelled upon installation you don't need a leveling compound. You do however need an adhesive compound and bonding agent. You can use a foam pad specifically dscigned for underneath hot tubs

If the surface is level and flat you can prime the concrete and to tile over, it'll be ok, but if the surface isn't flat or the level isn't acceptable you can lay latex (levelling layer) and put your tile after. You don't need to use any foam layer between the tile and bathtub

Blue Mapi water proof membrane and the screed to full area and and seal all corners eithe mapi tanking system let set yhen your good yo tile

You should be able to fit direct to concrete using standard adhesive. If fitted correctly you won't need any insulation between tiles and hot tub. The weight of the water in tub will keep this in place but make sure the tiling is done properly and laid level. As an extra precaution you could use an outdoor adhesive which has properties to allow for weather conditions.

This depends on the condition of the substrate. Realistically for external porcelain you would want to level the area if required, install a decoupling membrane as external areas are susceptible to temperature changes and therefore movement.
Porcelain tiles are generally pretty hard wearing so should take the hot tub well enough, but adding protection between the tile and hot tub is never a bad idea.

I would check the thickness of the concrete sub base and it possible the build up underneath it. If its sound and the surface is flat use a deep notch trowel to apply adhesive to the floor and thinly back butter the tile before laying. Anything between the hot tub and tiled floor i would seek advice from hot tub supplier