Plastering/renovating garden wall (outside) - but how?

Hello everyone.
As a layman, I wanted to get some information from you and thank you in advance for your many tips.

I want to replaster the garden wall. The wall is exposed to rain/wind and weather.

After I removed the loose plaster, I have the following questions:

1. With what should I plaster the wall? Mortar, renovation plaster, lime, etc.?
2. Do I need a primer before plastering?
3. What do I do about the curve? I have seen that there are only angular wall coverings.
4. At the base, I also wanted to attach a panel or something like that. Does that make sense? As a protective edge or something. I wanted to extend the small bed for the roses continuously since I want to plant the ivy.
5. I wanted to largely avoid decorative plaster since I want to green the wall with ivy. Do I have to plaster the wall with decorative plaster after plastering?

Please keep in mind that I am an absolute layman but would like to venture into something like this.

I am really excited.

Thank you.

I am also a layman, but I have an idea. First, chip off the old stuff if it is loose. Then apply [Sockelbeteich] with sealing slurry twice, then spray mortar against the wall, using a brush to prevent splattering, let it dry, then plaster with mortar. Possibly paint afterwards.