max_queued_messages_set(size)

[Julz-afk]

I am using python Paho client on my raspberrypi CM4 module. I have a question on the offline queue "mqtt_client.max_queued_messages_set(100)"

1. Will this queue only start to fill up when the connection to the broker is "disconnected" ?
2. When a message did not go through successfully to the broker will the message append to the queue for retry later ?
3. Is there a way I can monitor this queue, I want to get the length and if power fails I want to dump to local storage before powering down?

I have verified, I am using the latest version of Paho-client, Python and Api version 2 in the paho client.

I checked forms but couldnt find anything at this stage, will continue my search but hope someone could assist me , or point me in the right direction.