There are 2 ways :) here's how to do them...
Hard Way:
Keep going on walks every 30 mins.
Easy Way:
get action replay
Yes... You just have to get Action Replay Ds/Ds lite.
No but there is a way to make everything easier Make your dog wear the lucky collar
No, the Briard is not available in all version of Nintendogs and Nintendogs and Cats.
No. Unfortunately Nintendo added no weather to the Nintendogs or Nintendogs + Cats games.
No, because Pokemon is not in Nintendogs.
No, the Kelpie is not available in Nintendogs.
It is not possible to get a trampoline on Nintendogs.
Nintendogs happened in 2005.
No, the Afghan Hound is not available in all version of Nintendogs and Nintendogs and Cats.
Sorry to disapoint you but you can not get a leopard on nintendogs. Sorry :(
Nintendogs Game ID
Right now there is no information about Nintendogs 2.