Dragon's den in Johto, You'll then fight Clair and Lance with the Rival
by mt.moon on a monday a Pokemon leaves it behind hope this helped :D
He'll be at Mt. Moon, then the Dragon's Den, then you can't find him anywhere else until Sundays and Wednesdays at the Pokemon Leauge.
no pokemon
Cherrygrove City, Azalea Town, Burned Tower, Goldenrod City Underground, Victory Road, Mt. Moon, and the Pokemon League (Mondays and Wednesdays).
Pokemon league After beating him in mt moon Go up the stairs Untill your rival comes NOTE: he is only there on certain days this also works for heart gold
You fly to Pewter city and then go to the route on the west. Get through all the trainers, and after that, you should be able to go up into an area where there is a Pokemon center and a cave located near it. The cave is Mt. Moon, but don't go in Unprepared! Your rival will fight you as soon as you enter.
He goes to the Pokemon league. after that he goes to mt. moon or at least that's what happened to me.
monday between 20:00 and 23:59
That depends. Pokedex: Your rival at Mt. Moon. For your own: Trade a Kadabra.
a moon ball
You can't. New Moon island is in Sinnoh.
he's only there until you defeat him in a pokemon battle. then he leaves.