What are the 3rd genaration Pokemon that can't be obtained before the elite 4 in sapphire?

Question

Like Beldum.

Answer 1

Beldum, Metang, Metagross, Latias, Rayquaza
Seedot, Nuzleaf, Shiftry, Mawile, Zangoose, Solrock, Latios, Groudon, Jirachi, and Deoxys can't be obtained before beating the Champion, but they also can't be obtained after.
Huntail and Gorebyss are also unobtainable if you count trade evolutions as unobtainable.
Regirock, Regice, and Registeel can be obtained before going into Seafloor Cavern.
source

Comments

I thought Jirachi wasn't in RSE? I read somewhere today that Rayquaza can be caught before the League. Huntail and Gorebyss shouldn't be there because you can evolve them by trading with a friend "before" the League. Here states the Regis can be obtained before the league: https://www.wikihow.com/Catch-the-3-Regis-in-Pok%C3%A9mon-Sapphire-or-Ruby - Now remember, MightyMagikarp is talking about Sapphire only.

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Rayquaza can only be caight before the ege in emrald

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Jirachi was a Generation 3 Pokemon. It wasn't in RSE, so it can't be obtained anytime, including before defeating the champion. Therefore, it goes in my answer.
Rayquaza can only be found in the Sky Pillar, which is locked until after the player defeats the champion.
Every Pokemon, including these unobtainable ones, can be obtained by trading with a friend. I don't see how Huntail and Gorebyss are different.
The second-last line was a correction to your answer that lists the Regis.

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Okay. <space>