Reach the Sega Area Uptown stage in quest mode to unlock the "Old" versions of the stages. Hold Start at the versus mode stage selection screen while choosing a stage to select them.
Fight as Dural:
In quest mode, you must first reach the Sega Area Uptown stage. Now, in the shop, you must purchase the ability to fight as Dural. You will now be able to play as Dural in VS. mode. Move the cursor to the top left space to highlight and choose Dural for the battle.
Dural's eyes glow:
You will be able to fight Dural with her eyes glowing if you go into battle with her with your number of ones ending with the digit 9 when you reach Dural's stage in Arcade mode. (9,19,29,39, and so on).
Dural's second stage music:
If you reach Dural's stage in Arcade mode in less than 9 minutes you will hear a differnet music theme than you normally hear.
Fight invisible Dural:
This one takes a little math, but nothing that's too hard to figure out. Fighting an invisible version of Dural depends on you reaching Dural's stage within a time limit that depends on the following formula.
(#of rounds x2)+2
With the default setting set, the time limit is 6 minutes.
Hold Circle before the Sega Logo appears while the game is starting up to hear the original "Sega" Audio from the classic game Sonic the Hedgehog.