You can delete it by clicking it and pressing delete duhhh -miraih snipes
like Pokemon soulsilver and heartgold, you press down on the control pad, the select button and then b button.
by relessing it
You press 'Up' on the control pad , press 'select',and then press 'B' at the same time on the title screen to delete your save file.
you can't i tried trust me. if you did delete your saved file and you had a Pokemon in the walker it will be there until the battery dies get a new one.
To delete the file: Select+Up+B at the menu screen. Start a new file: Just press "New Game"
To delete a game file for any game, you need to press Up on the control pad, then Select, then the B button. But if you've got mewto or anything else good trade it with a freind and when you make a new file trade back.
go to release
you cant delete your Pokemon from your party directly but you can deposit them into the PC at the Pokemon center or you can release them if you wish to get rid of them the option is in your PC i do believe.
Hold B, Select, and either Left or Right.
Up, b, and Select all at the same time. :)
you can't
On the title screen, press Up, Select and B together. This will permanently delete your file.