I've debugged my tama before. I used my old V1 and V2 just in case and the both didn't break. First, you unscrew the screw that gets to the battery. Take out the battery. Second, Unscrew each of the tiny screws in each corner (with a glasses screwdriver) and gently take that part off. Find the dot or dots that say debug above them. "Color in" the little circles. (Rub them on about 7-10 times). Screw it back, put the battery back in, put the battery cover on, and reset it. The egg might look a bit weird. When it hatches, if you press A, you can choose whatever character you want (plus some cool debug characters!) Or just keep it as it hatched. To fast forward it (make it grow faster) Press C.
Hope it Helped!!!!
WARNING: If you do this, you risk breaking your tamagotchi! Do all the steps very carefully!