>>55447412Let me break it down for you
>GEN 1>MAINLINE GAMESRed, Blue and Yellow (could freely trade and battle between each other with no restrictions)
>SIDE GAMESStadium (could interact with RBY through trades and other features but not battling)
>GEN 2>MAINLINE GAMESGold, Silver and Crystal (could freely trade and battle between each other with no restrictions)
>SIDE GAMESStadium 2 (could interact with GSC through trades and other features but not battling)
>GEN 3>MAIN GAMESRuby, Sapphire, FireRed, LeafGreen and Emerald (could freely trade and battle between each other with no restrictions)
>SIDE GAMESColosseum and XD Gale of Darkness (could interact with RSE and FRLG through trades and other features but not battling)
>GEN 4>MAIN GAMESDiamond, Pearl, Platinum, HeartGold and SoulSilver (could freely trade and battle between each other with no restrictions)
>SIDE GAMESBATTLE REVOLUTION (could interact with DPPt and HGSS through trades and other features but not battling)
>GEN 5>MAIN GAMESBlack, White, Black 2 and White 2 (could freely trade and battle between each other with no restrictions)
>SIDE GAMESuhh... Conquest I guess? Rumble Blast?
The Dream World might be the closest thing to the Stadiums it had.
>GEN 6>MAIN GAMESX, Y, Omega Ruby and Alpha Sapphire (could freely trade and battle between each other with no restrictions)
>SIDE GAMES*cough*
>GEN 7>MAIN GAMESSun, Moon, Ultra Sun and Ultra Moon (could freely trade and battle between each other with no restrictions)
>SIDE GAMESRed VC, Blue VC, Yellow VC, Gold VC, Silver VC, Crystal VC, Let's Go Pikachu and Let's Go Eevee (VC games couldn't interact with SM and USUM directly but Pokemon bank allowed them to transfer Pokemon; LGPE could transfer directly with SM and USUM but once again, not battle)
>GEN 8>MAIN GAMESSword and Shield (could freely trade and battle between each other)
>SIDE GAMESLegends, Brilliant Diamond and Shining Pearl (can only interact with Pokemon Home)