Is a gravel foundation / retaining wall required for the structural stability around the house?

Hello,
a question regarding the design of the outdoor facilities. The base slab of our house sits on compacted gravel. Since the terrain has a slight slope, the gravel foundation on the south and east sides protrudes about 60-80 cm above ground. I want to clad the gravel mound on the side with a dry stone wall made of Buntsandstein. For this, I want to narrow the originally 1.50 m wide gravel border. Only 60 cm of gravel should remain, and the dry stone wall should be on the outside. I am aware that this will have no structural impact. Between the row of stones and the gravel, gravel will be reintroduced and compacted manually with appropriate hand tools (manual compactor and heavy sledgehammer). 60 cm of machine-compacted (compacted before house construction) gravel will remain outside the base slab, then another 20 cm of manually compacted gravel up to the dry stone wall. The dry stone wall consists of only one row of stones about 20-30 cm deep.

My question: does anyone have experience whether the 60 cm wide, compacted gravel wall is structurally sufficient on its own or if it must be secured with, for example, L-shaped stones? Could the gravel mound loosen or shift over the years?

Thank you in advance.

60cm height at 60cm width is 45 degrees. It can hold on its own, but not with a large additional load. Accordingly, the dry stone wall plays a bigger role here. If it is well made, it will certainly hold. As a layman on the first attempt and only with hand tools, I would prefer to keep a bit more distance. The area can be nicely designed with appropriate plants, that’s how I do it (still a work in progress).

With the dry stone wall, be sure to pay attention to a proper backward slope; picture 2 looks more like the opposite to me, with one stone even having the existing slope to the back equalized with gravel. This can be pushed out by frost after a few winters. Then the house will only stand on the gravel layer without support.

How was the foundation made? Strip foundation? Or just a foundation cushion made of gravel?

If foundation cushion, then you should only approach that with a professional. If you do something wrong, the house can settle.