Yes, but you have to start a new game.
It's impossible to play as anyone but Samus in the adventure mode even with cheats since that may screw up the storyline. However, if you have faced another hunter in adventure mode, you can play as that hunter in multiplayer mode.
yes
No
play adventure mode as megalon
You play and finish adventure mode a second time
Play from an hour then do adventure mode.
In adventure mode, finish the first level with the time limit having a 2 in it. To unlock Luigi in the first game, you must complete target test with all other characters. In brawl, you have to complete Classic Mode on Easy with no continues, play 22 brawls, or get him to join you in the Adventure Mode (The first two ways, you will have to fight him to unlock him [In Adventure Mode, You will not have to fight him.]
in story mode 2 in online mode 2/4
In story mode, only one person can play. In multiplayer attractions mode, up to 4 players can play.
You play and finish adventure mode a second time
Play pool adventure mode or play survial pool ... I think
To get all the statues you must play story mode aka adventure mode.