How do you get Lugia, mewtwo, Mew, and seedot?

You cannot catch a wild seedot in this game, you must trade from a ruby to a sapphire, and vice-versa (with lotad) along with many others. As for the others, you must use an action replay or gameshark to get them.

You have to use a cheating device,like a gameshark/action replay.

None can be found on Sapphire normally. The first three must be traded, and Seedot can either be traded from Ruby or hunted for after mixing records with Emerald following a broadcasted breakout.

Lugia: Buy, rent, or borrow Pokemon XD Gales of Darkness and get to the end of the game and use your master ball on Shadow Lugia. Then put it in the purification chamber and make the whole thing perfect. Shadow Lugia will be purified. Now go to the Pokemon center at the water and dessert town (I forgot the name) and trade it to your Game Boy Advance game.
Mewtwo: Buy, rent, or borrow Pokemon FireRed or LeafGreen and beat the Elite Four, then go to the cave that was blocked. At the end of the cave, catch Mewtwo and trade it to your game.
Mew: There was an event that just passed at Toys R Us that downloaded Mew into your game. If you missed that, use an Action Replay or Gameshark. If you don't like to cheat then wait for another event. (which could take years)
Seedot: Catch it on one of the first routes on Pokemon Ruby, then trade.

I don't know about the others but it is posible to cath a seedot on sappire it's very hard though.

You have to go to the home town and then follow the trail to the first city then follow the trail to the second city you will see a tree juting out of the forest go to it and then search the grass entile you find one.

And again it is very hard to find iv only done it once

I just started but none of thease helped thay all suc hairy monkey balls *******