When you go to genoration 2 on a v3...

[Gingerkitty]

does your souviners stay? or do you have to get them back again? and what about the royal costume? would it stay?

 

[Atlantic]

all the souviners stay unless your tamagotchi dies

 

[peeweebird_123]

You keep your souveniers/items/points/etc... but I think there is a "bug" in V3. Some of the souveniers disappear after a while. <_<