The 2nd edition and the 4th edition settings have some important differences, and that was reflected in the monster manuals for both. The 3.5 Monster Manuals (Terrors of Athas and Terrors of the Dead Lands) were compiled from all the sourcebooks from the original setting and all the splatbooks, along with a few monsters that were in the two videogames released that didn't appear in any guides (I.e The Mountain Stalker).
The 4th edition Monster Manual had some pretty big differences from the 2nd and the 3.5 monsters (Such as Thrax not being undead). So I would treat them as two separate books, as the 4th edition update ignored most of the second edition expanded world, such as the Dead Lands and the Last Sea.
As for lycanthropes on Athas, there is one creature from 2nd/3.5 which fills the role of lycanthropes under the dark sun, The Pakubrazi.
Athas is surrounded by The Gray, which is the final resting place of souls and makes travel to the outer planes very hard. Therefore, theres not much point in fiends going to Athas (they exist to tempt or force mortals into sin so their souls go to the plane of the fiends allignment, so whats the point of going to Athas if there are no souls to claim?), so there were no Tieflings in 2nd edition. They were a playable race in 4th though.