You can call certain ones depending on what day it is.
You have to beat 16 gym leaders and beat elite 4 in kanto and johto to beat the game.
You cant get a rematch in diamond and pearl that I'm aware of. Not sure about ruby/sapphire though..
Walk in and save the game then go in and in out
He vanishes from the game until the next day, were he is in the same place for a rematch.
On eather game, sadly, you can't. But on Diamond, Pearl, Platinum, Heartgold and Soulsilver you can...
beat all the gym leaders in kanto and johto and all the elite four you will meet him at the very end of the game at mt. Silver
You have to beat red in order to beat the game.
You must beat Red, the game's version of Ash, at the top of Mount Silver.
Yes but after a full game week he will come back you can rematch him over and over again this is perfect training for your strong pokemon.
You cannot rematch just any trainer, there are only certain trainers that you can re-battle such as the 4 Elite 4 trainers as well as Alder. Additionally you can rematch the trainers at the Big Stadium and the Small Court in Nimbasa City, you can also rematch Cheren in Victory Road, Bianca in Professor Juniper's lab, Cynthia in her Villa in Undella Town, Morimoto in the Game Freak building in Castelia City and the Royal Unova trainers.
Uh how about buy a new game.
there is another region in the game that is red version and you have to beat all the gyms.