features of the HOMM3 game

You're a dirty player. I summon you! Calm down, take a closer look; it says FEATURES and TRICKS of the game, and the heading is TIPS. Not all players know about the tavern teleport and so on. This wasn't intended by the game creators; players discovered this trick themselves, and I'm more certain that you learned about all this from someone or from sources. I doubt you figured it out on your own! A unit attacked by a Basilisk is under the Stone Skin spell, not a shield. Here's a tricky question for you: a Greymane Golem has 40% magic resistance; how does this resistance work, since there's a specific algorithm?

Hey, Chuvi.
Everyone couldn't care less about how this resistance works for Golems because Golems aren't used as main attack stacks, and therefore you won't see them in battles except as meat shields. And they're excellent meat shields, with a lot of HP and, thanks to having some kind of ability, they're a great choice for soaking up damage, especially against Griffins.
You'd be better off practicing and learning to play using templates, attacking the Guardian on the second day, taking max Golems on the first day, and so on, instead of wasting time with nonsense and asking about the dubious ability of Golems.