I spotted a fake tama in the free-market while my parents watched the stall.
Its shape and design looked something like this. But Instead of 'Princess Max' it said 'Infrared Tama, Ver.5' I doessn't even say what company it came from. And it is touch screen!
One way to recognise a fake tama is when you already know the appearance and function of it.
Real Tamagotchi V.5
Egg shape, three buttons
Bandai logo, Can raise a family
Fake Tamagotchi V.5
Princess Max shape, no buttons, touch screen
No Logo or logo of a company other than Bandai, Says something other than Tamagotchi (Infrared Tama)
And I'm sure it is a fake because it claims that it is real and has picture of tama's all over the packaging.
I hope this helps