Besser/Cinder/Masonary block retaining wall footings

I did a wall 4 blocks high across the back of the storage room behind the garage. Previous owner who dug it out merely "rendered" the remaining dirt (clay/shale) around 20mm thick, which promptly cracked & allowed a mini-landslide.

As it was only 4m across, I turned the wall 90 degrees at each corner & continued it for around 800mm (2 blocks, or 2.5 blocks on the intersecting corner), to add strength.
My footing was 600mm wide, and about 400mm deep, with trench mesh laid into it.
I hung timber props from the floor joists above to attach the upright reo bars to, which were bent in a J shape & wired to the trench mesh.
Once the footing concrete was set, the timber was removed to allow the blocks to be slid down over each bar.

Each block hole (2 per block) had a vertical bar in it, and I core filled each one (advice was to do every 2nd or 3rd, but I wanted a strong wall).
I ran a horizontal bar across the top of the 3rd course, tied to each vertical, and ground off those uprights to finish about an inch from the top of the last (4th) course.
It was a pain in the butt, but we mixed the core-fill in the mixer, and poured it one bucket at a time down each hole, working it well with a rod to "settle" it well.
Bottom row was laid with gaps between each block.

I put a thick PVC (an old billboard banner) behind the wall & backfilled it with gravel up to the top, then concreted by hand from the rear of the wall, back to the original ground level behind the wall, just to flush it off neatly.

I get a bit of weeping coming through the gaps after a decent amount of rain (groundwater/seepage) so I'm glad they are there.
The wall is extremely solid, and worth the effort.

On a longer run, I would consider a couple of engaged piers or runners back into the area you are trying to retain - like I achieved by having a 90 degree corner at each end that continued for a bit.