When you nickname your Pokémon, that Pokémon's new name will appear in your roster, any battles, basically everywhere.
You can rename any Pokemon which YOU originally named by heading to the Name Rater in Goldenrod City (gen 2 Pokemon games). If it was gotten from a trade, in or out of game, it cannot be renamed.
Nothing Happens
nothing happens unfortunetly
nothing happens.
You actually get to name your rival. So, your rival is whoever you want him to be. The rival is just a strange character that happens to be eying Professor Elm's Pokemon.
You are a Pokemon master.
Nothing happens.
you can't
Nothing happens you just trade him and he leaves and you go on with your Pokemon journey
nothing happens
You can't die, if you mean what happens if all your Pokemon are fainted, you just go back to the last Pokemon center you've visited.
Then you have a level 70 pokemon!