Z3 model d6683: dual sim both 3g and 4g too?

Hi,
my name is Andrea and first of all thanks to give me your attention.
I'm in europe, italy, and was watching Z3 model d6683, it's for chinese market i guess, particular version of dual sim model. Now, i've two sim, the operator is "3 italia", and its signal is from 3g to 4g (if the area is covered by 2g signal only, i go in roaming signal, and can't surf etc). Now, i'm looking for a dual sim phone, and both sim have to get at least 3g signal at the same time. I'm not asking to surf with both sim at the same time, and i'm not asking "dual active", not interested if when i call, the other sim goes airplane mode. I'm asking if Sony Xperia Z3 model d6683 has two sim can get both at least in 3g mode during standby and always in general, cause i surf with one sim, i call with the other one, but this last don't want to go roaming all the time. Hope it's clear.
I can get this particular model because an Eshop has it online, but first need to know this problem.

Hope it can, and battery can last in any case.

Or if you know some other phones...

Thanks