Answer:
first for the rexy dog just use stygy pachy and spinax or alectro you can find alectro in bottomsup bay and when you beat rex and you go to snivels use amargo you can find at mt lava flow and if the big boulder is not gone you can still find him before the big boulder.and when you beat snivels use the same guys to beat vivian you used to beat snivels.hope i helped