Is dualband WiFi at all logically possible?

Installing and Using OpenWrt Network and Wireless Configuration
9

Solved it, thank you. Works like a charm. Here is my HowTo:

It can't be if the phone is not rooted. You can not control WiFi connections with an app.

Then I will not have the bigger distance advantage. Perfect solution is:
distance: 1m------10m------20m------50m------100m
bandwith: 5GHz--5GHz----5GHz----2,4GHz--2,4GHz