Sites like Obozrevatel School provide full solutions for each problem number, including theorem proofs and logical steps.
Most editions feature 6 variants divided into three levels of complexity (A, B, and V/C). otvety na kontrolnye po geometrii 8 klass ershova
You can find digital versions of the collection on sites like EGE-OK or Grot-Matem . Sites like Obozrevatel School provide full solutions for