Newbie questions on passive implants, breeding inheritance, and cave respawns

The poster, a newbie, asks whether passive-skill implant surgery only swaps existing passives or can also add one to a pal with none, and whether both parents' shared passives always pass down during breeding. They also ask whether breeding a shiny (community slang borrowed from Pokémon for rare color-variant pals) parent with a normal one produces a shiny child, whether implanted passives can be inherited too — potentially letting a desired passive combo be endlessly copied — and when cleared caves respawn, including whether same-named caves share a respawn cooldown.