could I move around 4 citys as one in rush hour??

[skaaater 0]

If I conjoined 4 citys to make a metropolis,could I move around these 4 citys as one. You know, not having to got to the region and load a different part of my metropolis. (a different tile).

[GDDan 4]

unfortunately, no. its the same in RH as with vanilla

[MadMax410 1]

Im pretty sure you can't. But you should do that anyway, for you can make better cities.  

[sim1234 62]

No you can't I'm afraid.There are only 3 city sizes Small,Medium and Large and you can't conjoin or separate cities.