If your pond does not freeze solid, and if you leave a hole open
in the ice, turtles will be fine in the pond over winter. I'm in US
zone
7, often four inches of ice on the pond, and my turtles wintered
over (painted and red earred sliders).

As for frogs - they go into a hibernation like state - Get them cold
enough and they slooooow way down - and different
species have different ways of going thru the winter.
I have pacific chorus frogs who hibernate in leaf litter and under
debris and bullfrogs who go thru the winter in the pond.

k :-)