The Great Wheel Cosmology comes in, roughly, five separate generations:
- The first generation, laid out in Dragon Magazine #8 ("Planes: The Concepts of Spatial, Temporal and Physical Relationships in D&D", July 1977), the AD&D Player's Handbook (Appendix IV, 1e, 1978), and Deities & Demigods (Appendix I, 1e, 1980).
- The second generation, found in the AD&D Manual of the Planes (1987). Mostly a systematization and rationalization of various bits and pieces added to the first generation through adventures and monster entries, its big contradiction is throwing out three of the Paraelemental Planes from Deities & Demigods in favor of new ones. Also used in brief in the pre-Planescape printings of the 2e DMG.
- The third generation, Planescape (1994). Grabbed and ran with the Blood War concept from the 1991 Monstrous Compendium Outer Planes Appendix, unified the alternate Material Planes into one single Prime Plane based on Spelljammer (unifying GH, FR, and DL to being on the same plane), made various changes (like to how the Plane of Fire worked) to improve adventuring in the planes.
- The fourth generation, D&D 3rd Edition Manual of the Planes (2001). Now demoted from the cosmology of everywhere to merely one example cosmology (undoing the Spelljammer/Planescape unification of FR, GH, and DL being on the same plane, since now FR was in its own cosmology), reworked how the Astral worked to match how 3e spells worked, decanonized the Paraelemental and Quasielemental Planes.
- The fifth generation, D&D 5th Edition (5e Dungeon Master's Guide, 2014). Still an example cosmology. Redefined the Elemental Planes in a way that hybridized the 4e Elemental Chaos, the vast pure elemental expanses of the early AD&D Elemental Planes, the elemental echoes of the Prime seen in BECMI and kinda-sorta in the Planescape/3e Plane of Fire, and the Second/Third Generation Paraelemental Planes.
If you try to integrate between generations, you will absolutely and certainly find contradictions. If you try to bring in stuff from BECMI, the alternate cosmologies in 3rd, and the 4th Edition World Axis, you'll get even more contradictions. Since Forgotten Realms used the first, second, and third generations of the Great Wheel, then its own World Tree (and, technically, simultaneoulsy additional csomologies depending on what part of the Realms you were in), and then the World Axis, and now seems to have defaulted to the fifth generation of the Great Wheel, its cosmological lore is
utterly full of contradictions.
Incidentally, the number of godly ranks increased from Demi/Lesser/Greater in 1e to Demi/Lesser/Intermediate/Greater in 2e, and there was never a clear definition of how to progress between the ranks (there was one Dragon article in 1e that was always dubious, there were occasions where gods were declared to have changed rank, and the 3e Deities & Demigods had very fine-grained divine rank mechanics without canonical advancement rules). Primordials were introduced in 4th edition, with some earlier gods retconned into them.