He doesn't actually go anywhere...he just dissappears...
If you want to rebattle him then re-defeat the elite for (ths can be done at anytime) and climb Mt Silver and he'll be there again. His Pokemon stay the same but still they are handy for levelling up yours.
Congratulations for beating him, he's tough :D Beating Red is lot's of fun and great for training, I've defeated him about 5 times and it's always a great challenge even for my lvl 100s
Hope this helps :D
you find it in mount silver when you've beat trainer Red 3 times
beat the Pokemon luegue then go to the Pokemon centre
nothing
All It Does Is Add One star To Your Trainer Card
after you beat the gym
Any Pokemon 70+. RED'S Pokemon are Pikachu Blastoise Snorlax Lapras Charizard Venusaur
you find it in mount silver when you've beat trainer Red 3 times
With Pokemon.
I did lol Leader Jasmine did
he just trains with his trainer
Pikachu
You get another coloured trainer card. If it's gold, you get a black Trainer Card.
an easy way is to trade a bunch of your good Pokemon onto Pokemon heart gold but if you don't have a lot of good Pokemon on heart gold and you don't have another game then train a lot before you get there :)
go to prefacer.oke then you get one stear pokemon
Have about 2 or 3 pokemon only. If you fight every trainer you should be okay.
You finish Pokemon heart gold after you beat red.
beat the Pokemon luegue then go to the Pokemon centre