Select victory pose
Just press the Kick or Punch button after you win a round to switch your victory pose.

Switch starting characters
When your between matches, hold two Kick buttons. When the match starts, you can begin the round with your second selected character instead of your first.

Fight against Shin Akuma
Finish the game once with each character, except for Pyron successfully. Then Shin Akuma will appear after Pyron is beaten when you are using a team containing your last set of characters.

Or you can simply finish the game in arcade mode in any difficulty setting, winning every round including those against Pyron. Also you need to have at least two Perfect finishes and at least one super combo finish in each match. Then Shin Akuma will appear after Pyron is beaten.

Fight as Shin Akuma
Simply beat Shin Akuma in arcade mode.

Classic character sound themes
Finish the game to have classic themes available for the characters used in the "Sounds" option. To have Shin Akuma's music available, beat Pyron as Shin Akuma.

Fight as Pyron
First beat Pyron in arcade mode. Note: You will also have to access his stage.

Fight against Ingrid
Be the victor in each round of your first three matches and have at least one perfect finish.