River crossing scenarios?

[Crossroads]

Back to these rivers and bridges with a bunch of new questions...

- What is the fundamental difference between a heavy full hex bridge or a heavy full hex pontoon bridge?

- How heavy must a pontoon bridge be to allow for medium tanks, is there a way to create them so that heavy tanks cannot cross (IS-2s, ISU-152s), but the said medium tanks e.g. T-34 SU-76 let alone T-70 can do so?

- Can either one (full hex bridge, remember) be damaged , or are they basically the same, just visually different?

(I have learned about putting a deep river with a hex side bridge to both hex sides, these can be damaged in a normal manner, this is not what I mean. I am asking about the full hex bridge itself.)

For historical reasons I will need both real bridges and pontoon bridges, but is there a difference how they should be used during the scenario?