how come when you a baby you gat one game then when your a kid you get another game but when you become a teen you get three games and they are all on the same page?
Yes, I think it's to save space. There being five games, BanDai would either have to get rid of one or put them over three pages (both not as convienient) to avoid three on one page. It's just the way that the V4 is put togehter.
As your Tamagotchi character gets older, s/he is capable of playing harder games. Same as real life - you wouldn't expect a two year old to be able to play Monopoly and Crazy-Eights but you might be able to find a two year old who can learn to play Hop-Scotch.
Also, the grouping of the games is logical. The two on the same page award skill points in a random category. The three on the same page award skill points in specific categories.
This is just the way tamagotchi's work. The 3 games on the first page award a specific type of skill point all the time. The other 2 games can award any type of skill point.