Sega Master System / Mark III / Game Gear
When you reach a special treasure pot, hit it so that the bonuses fly out, collect the extra life and walk off the screen, then walk back to the chest to collect another life. Continue this until you have enough lives to complete the game.
On round 1-1 as Obelix, go into the first well, and stand on the platform at the left of the screen. When it falls, walk left to go through a wall into the room.
Play as Obelix in round 2-1, jump onto the rotating platforms to the Menhir container, then jump to the platform on top. Do small steps where there isn't grass and you will suddenly fall into a secret room.
There is a level select but it has been deliberately removed from the final ROM. There are several ways to reinstate it:
00at ROM address
The game returns to the title screen after each level.
See the main page for Astérix