OK, the Frog came first, great buggy.
Bugaboo then decided to discontinue the Frog and introduce the Cameleon and Gecko.
Basically the Cameleon has more features than the Frog (but is essentially the same design) - telescopic handle, adjustable suspension on the little wheels, slightly larger shopping basket underneath, slightly longer seat unit (5cm), different apron on the carrycot and the addition of an Aerosleep mattress.
The Gecko was again like the Frog but with fewer features to make it as small and lightweight as possible. A pared down version if you like. A smaller seat frame and fabrics, a different method of changing the seat angle (no white circular buttons on the sides).
The Gecko has now been discontinued due to lack of popularity and the Bee has been introduced as the super small lightweight option.
The Bee is great, a very simple to use city buggy, but suitable from birth. Rear or forward facing, folds in one piece, decent size shopping basket, v good for its size.
All Bugaboo models are compatible with the Maxi Cosi Cabriofix.
I loved the Frog, it was a classic.
AFAIK it is still available in the USA but not anywhere else in the world.