In three of a kind rule, can I play for example 1 cat card and 2 clone cards to make a three of a kind card ? or 2 nope cards and a clone card to make a three of a kind card and so on ... so the ultimate question is : can clone card be used in two of a kind and three of a kind combos ?
Yes this works, there's a little explainer in the rules for the Zombie expansion underneath the base clone instructions (emphasis mine):
You can play a Cat Card with a Clone to create a pair and steal a card (because the Clone becomes the same card as the Cat Card you put beneath it). This only works if you are the player who played both the Cat Card AND the Clone―you could not play a Clone on top of a Cat Card played by another player!
The game doesn't specifically mention the 3 of a kind triplet combo, just the two of a kind pair combo, but since they both work in the same way, just with more cards played together, it's probably safe to assume the 3 of a kind combo works the same way.