Number of Wi-Fi channels to be used?
It has nothing to do with battery life; the number of channels is a regulatory issue (for example, in the US, only 11 channels are allocated for 2.4GHz Wi-Fi).

Technically, Wi-Fi is frequency hopping, so the "channel" is a center frequency around which the actual transmit frequency skips.  You can't disable that; it's part of the channel sharing arrangement (Wi-Fi would be unusable if every client on the channel transmitted on the same frequency).  And beyond that, which channel your device uses is determined by what AP you're associated with, so you have no control over it.