Assume you have saved a product in the Catalog. Will your last changes be taken into account for rule-based
related products?

A.
Only if you go to the “Catalog/Rule-based Product Relations” page, and hit “Reindex All” button.

B.
Only if you clear the cache.

C.
Yes: It will be done automatically by an observer on the catalog_product_save_after event.

D.
Yes: Rule-based related products are calculated on-the-fly.