I got into a Pokémon battle and ended up wasting a huge amount of my supplies only to end up losing the battle and the Pokémon. Is there a way for me to reload a previous save so I can try again and maybe change the outcome of the battle?
You could quit the game and load it back up but the game has an autosave feature to prevent you from cheating like this. The game doesn’t want you to have a second try if you fail a battle.
From the pause menu, there is no load game save option, just the ability to save. So shutting the game down as quickly as possible is your only option.