Dual Sim - Dual 3g/4g? Or 1 slot 2g and 1 slot 3/4g?

Fairly simple question, but I cannot find definite information. Maybe I'm just looking in the wrong spots.

Does the Luma 640 Dual sim support 3/4g in both simslots?

What about the 640xl, 650 or 950(xl)? Does any of those phones support dual 3/4g sims?

Thanks :)

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