On a spackled wall, tiles or plastering

I have completely renovated and plastered a room, but afterwards I now want to install tiles and apply a lime-cement plaster in the upper area. Because of the plastering, the wall is now completely smooth... will the plaster or tiles hold on it, or do I have to sand it down again or just roughen it? Thanks, best regards

Tile adhesive also adheres to a plastered wall. However, you must at least prime the substrate. Get advice where you buy tiles. But lime-cement on a gypsum substrate is not recommended. It will probably become too hard. However, there are also thin-layer plasters that can be applied to gypsum. I would rather stick to the same material or remove the gypsum.

and apply a lime-cement plaster in the upper area

I wonder why you want to do that? Putting tiles on the bottom is no problem - prepare the substrate (e.g. primer) and put them on. At the top, I would simply apply a nice finish.