Here are the different modes available in the game. I'll only talk about the "secret"/interesting modes, namely:
TekkenForce, Training, Tekken Ball and Theatre mode.

NB:-SECRET- means this mode needs to be unlocked. It won't be available when you first start.

- TekkenForce (TekkenShuu) mode -

A sidescrolling beat'em up! 4 stages.
System: you lock on an opponent, and don't lock off untill he's dead. At the end of each stage, you fight a boss (one from the "not secret" characters, presumably.
During the stages, you will get life'ups (food), time bonuses, etc...
The enemies you'll meet (small scrubs known to this day) are Falcon, Crow, Hawk and Owl.
Each time you finish the game, you get a key to the undergound. Get three keys, and the next time you'll get a chance to fight Dr. Boskonovitch to free him.

- Training mode -

The new practice mode has 3 different parts:
- Free: will let you beat up your a "dummy" opponent, letting you set his actions (stand/crouch/guard...).
- VS CPU: as it says. You set the computer level and the stage relative CPU AI.
- Combo training: shows you the 10 hit combos for all characters, and juggles for a few of them.
For all modes, you can turn on/off the following options:
- Counter attacks.
- Freeze signal (the characters are green when the pad can influence their actions, and turn red when they are "freezed").
- Attack data (shows damage counter, combo counter...).
- Replay settings (determines when a replay occures). - Key display (shows you the pad actions on screen).

- Tekken ball mode - -SECRET-

Play beachball using Tekken combos!
Each character is in his side of the field, and a ball is set in the middle.
Hit the ball with a fierce move, and it will charge with the "damage potential" of the move (indicated at the bottom of the screen), and fly to the oponent, lit with your specific "spark".
At this point, the oponent can do three things:
- Hit it with a small punch, or guard it, simply sending it back.
- Hit the ball with a fierce move, thus charging it and sending it strainght to the attacker. He is then given the same choices.
- Throw the ball. It's a kind of "special move". This will cause it to "chill", and bounce up and fall down slowly at you. Now if you hit it lightly it will fly up and come back to the attacker quickly. Otherwise, it stays "chilled" and will do that next time someone hits it with a light move. It 'unchills" when it is hit by a fierce move again, or falls down/hits oponent.
All this time, the ball keeps it's "damage charge" for each character. It uncharges only when it hits someone, or hits the ground besides the limit (about 1/3 of each side's playfield).
One last special feature is the "fireball": when the ball is charged to the max, it will be set on fire, and when it hits the oponent, it does 100% damage, and does a 7-times quick replay! (normal replays in tekken ball plays 3 times...)

Unlock method: finish the game with the 10 base characters.

- Theatre mode - -SECRET-

You can watch all the movies you've gained and listen to the BGM musics. And if you've got tekken 1/2, you'll be able to watch their movies as well (hence the "disc" button).
Unlock method: finish the game with the 10 base characters to get the movies, and get all endings to get the disc/music option.