All terrains released before November 2019 are compatible:
Given the version number and “All Modules B…” — on torrent sites, you’d see “All Modules Bundle” or “All Modules Pack B” (sometimes multiple repacks: Pack A, Pack B).
If this is a cracked version, note that:
Plus all free instant action and single missions. DCS World v2.5.5.41371 Stable All Modules B...
It wasn't perfect. If you roll back to this version, expect the following bugs:
No issues with: A-10C, Ka-50, MiG-21bis, P-51D, or the Persian Gulf map. All terrains released before November 2019 are compatible:
This particular stable build represents the apex of “old DCS” before the 2.5.6 cloud/lighting fiasco and before the supercarrier monetization push.
It was:
If you’re running this version today (legitimately), you’re missing 5+ years of improvements: Plus all free instant action and single missions
If you are reinstalling v2.5.5.41371 today, note these hardware facts:
To move from 2.5.5 to 2.9: