All Weapons:
Draw pistols, step backwards, step forward, duck, stop ducking, turn around three times to the right, and jump backwards.

Level Skip:
Draw pistols, step backwards, step forward, duck, stop ducking, turn around three times to the right, and jump forwards.

Blow up Lara:
Step back, step forward, duck, stop ducking, turn around three times and jump backwards. Ouch.

Secret Room in Lara's Mansion:
When you enter the mansion go to her pool. Behind the diving board there is a switch. Press it to open a door in the main room with a switch behind it. Pull the switch and quickly turn around and sprint for the room across the hall. Inside you'll find some of the artifacts she's collected on her previous adventures.

Race key and Basement:
Go to the Library. When Lara walks in the doorway, there are two bookcases to the right. Approach the one on the left and press Action. Lara will pull a book and the fire will extinguish, allowing her to climb up the side wall inside the fireplace. After reaching the top, follow the passageways until reaching a room with two levels, with a switch on the top level. Pull the blocks in a way that a hallway leading into the attic is revealed. When Lara pulls the switch, the basement door will temporarily open. Quickly run through the attic, and down to the main hall to reach the basement. Once in the basement, walk through to the second room and look in the tank on the right side. Inside is the key to the race course. To collect it, pull the block in the other room to the center. Climbing up to that hall leads to the tank.

Thanks to Revolution readers The Cow, Alan, Paul Keating, Andrew Sallows, Dan Ross, Dadbones, Dian Zlatanov, Joacim Georgsson, Chris Davis-Shannon, Kyle Hill, Kazmawee, and Wolfgang Walek!