Castlevania: The Dracula X Chronicles Cheats

Annette is located in Stage 7. You first need to rescue Terra and Iris to be able to do this.

In the first room of the clock tower section, break the red pillar statue and push the switch behind it. Next, climb to the top where there's a small cog wheel and locked door in the upper right corner. Hit the cog wheel until the door opens and enter that. In this next area, kill the hawk to obtain the key. Hold on to it for now.

Next, in the last room of the clock tower section, you'll see a locked door. DO NOT USE THE KEY here (as its a fake room) and instead proceed upward until you see a crystal pillar blocking another switch. Like before, break the pillar to push the switch. Now go back down to where the locked door is. If done correctly, a new area should have opened up below with another locked door below the first one. Open the new/lowest locked door and after a cutscene, you'll save Annette.

You can come back here again in later playthroughs to find a room with several candles that drop moneybags and the Stopwatch subweapon if you're using Richter.

Richter's whip can be extended secretly!

If you press forward two times just after pressing the attack button, Richter's whip will extend slightly, making it easier to hit some enemies. You'll know it works when the whip turns white during the animation. It can also be done while jumping and crouching, you just have to hold the crouch button while pressing forward two times.

She's found in Alternate Stage 3:

Go through the stage until you get to the very end of the first half. You'll see your first door and a small plateform underneath that appears to be a dead end. Simply jump under the door and hit the wall, from the top to the bottom. Go down the stairs there and you'll save Tera.

She's found in Alternate Stage 4.

Simply keep going through the stage (do not go down the waterfall on the raft yet). Go all the way across this part of the stage until you notice a blue frog. Don't kill it. Instead jump over/avoid it and let it stay close. It will follow to the end of this particular part of the stage to a row of frog statues. It will jump on the only pillar that doesn't have a frong statue on it and lower a plateform in the middle of this section of the stage. Go down the stairs and follow the path until you get to the end where there is a gate. Iris is awaiting there.