Indiana Jones questions

I have several questions arising from Raiders of the Lost Ark, the first Indiana Jones film.

What was the biplane on floats at the beginning?

Did any ancient peoples ever realy build temples that had deathly defences such as scene in the opening sequences? It’s a great scene but seems rather far fetched.

The Solent flying boat seen when Jones goes to Asia was the one based at Oakland, California I understand. In the film it’s seen sitting in the water with at least one engine running. Then it’s seen flying in the map scene, though thismight be a model. Was it actually flyable back then when the film was made? It’s also a bit out of place chronologically but that doesn;t matter, lovely to see.