what are dividedinto4 groups,snakes and lizards,turtles,crocodilians and the tuatara.?

Answer 1

I suppose the question refers to the traditional "Class Reptilia".

However, the modern classification system does not consider such an assemblage as valid, because it's paraphyletic (i.e. it comprises some taxons to the exclusion of other more related taxa and their common ancestor).

All these animals are amniotes, i.e. tetrapod vertebrates that have extraembryonic membranes in a terrestrial egg.

However, turtles are anapsids while the rest are diapsids (although there's an hypothesis that turtles are derived from diapsids).

Among the diapsids, lizards and snakes are the closest relatives of the tuatara (both are lepidosaurians), but the crocodilians are part of a different lineage, the archosaurians. Birds are also archosaurs so they'd have to be included in this group.

It may be a little confusing, but to sum up, these are not actually 4 groups. Here's a cladogram (a representation of these groups):
http://kentsimmons.uwinnipeg.ca/16cm05/1116/34-20-AmniotePhylogeny-L.gif

You can see where the groups you mention "fit in" among the amniotes.

Answer 2

These are the 4 living orders of the class Reptilia

Answer 3

Huh? Not sure what you're asking...