A preset command is issued from our own platform. How long can this command be retained on the TTN platform without loss? Is there a specific value
Do you mean a downlink?
If so, it will only retained until it has been sent to the device.
PS, I’ll close your other thread so answer only appear here.
Our device can trigger to go online to receive the command by itself. I mean, our device will not trigger first. How long will it be able to receive the command after triggering, Or how long after the trigger does not receive the command
You program how often / when the device goes online - an uplink.
For Class A mode which is the most common, the device should listen for a downlink 5 seconds after it has finished the transmission and then again 1 second later. The 5 second is the default for TTN and is setup using OTAA, for ABP you have to set this in your device firmware.