1. Looks like current release does not allow update of uplink or downlink counter through commands. Only way currently is for device to send at least two uplinks after joining.
4. US uses 500k channels for downlinks. DR8-DR12 in the LW spec.
Each uplink will schedule two rx slots for possible downlinks. If a downlink does not use the slot another may use it.
5 b.) The packets will be queued for each node immediately, then they will be transmitted by cycling through the node list and transmitting a packet to each one. So i would not expect 6 to the first, then 6 to the second, but 1 to the first, 1 to the second,…