You don't have to, no. However, if you beat Red he will disappear from Mt. Silver. If you then beat the elite for again, he will reappear. There is no limit on how many times you can do this, but it won't make his, or the elite 4's Pokemon and different or better.
you need to faint and have one Pokemon in battle
you go battle bertha the second elite four member.
Go to the Pokemon center right outside of Victory Road and go in walk to the second area and battle the veteran trainer (Veteran Clayton), he has Lickilicky
I am pretty sure it was the Second Battle of the Marne but I am not a 100% sure. No, The Third Battle of the Aisne happened before the Second Battle of the Marne.
some trainers will register themselves in your poke-nav. after talking to them, and will bleep/call you for a rematch.
type in sadx trainer then click on the second link then get either trainer 3 or five peace suckers
You can battle Wally a second time after defeating the Pokemon League.
He is found before the second battle with jenova, or the reunion.
there was no second battle
the first one you go to jubilife city and beat him the second one is at hearthome city the next one is at pastoria city thenext one at Pokemon leuge and then at battle tower (tip)....... u can only battleur rivel at battle tower every Saturday and Sunday.
First, go to the second floor then go to the third floor using the stairs in the back. Use the secret switch on the statue and fall down the hole to the left of the scientist trainer. Now battle the trainer and go down. You should see a staircase to the basement.
123 is hippodown which you battle against in the elite 4 (the second trainer) and number 4 is chimchar which you can select for your starter but by the way it sounds your pretty far so you'll just have to battle somebody in the game who has it or trade a friend