Basic Configuration for Nocturnal Flight Call Recording

I took delivery of an Audiomoth 1.2.0 just less than a week ago and yet I am still having issues getting the recordings that I want ... or at least expected. I'm a retired IT engineer (40 years and old enough to have coded in 'C' :) ), with a couple of years experience in Bird sound recording and a good year or so's experience of 'nocmigging', so I thought that setting up the audiomoth would be a cinch. However it appears not to be so straight-forward, so apologies in advance if I have made some stupid 'newbie'assumptions and mistakes.

First mistake - Using the wrong type of USB cable - changed from a charging to a data cable

Second misstake - using the wrong type of microSD card (2 nights recording ending with a 'corrupted' SD card which needed re-formatting) - so purchased a Sandisk Extreme 64GB card

at the 3rd attempt, I got some recordings, but the files were of differing sizes and generally hadn't captured much in the way of bird calls or even household noises, apart from the first file, generated after the device started recording at 19:00

This was not what I had expected - as the config tool told me that the device would generate a series of files around 230Mb in size.

Question: Does the audiomoth only record when a sound is detected, or do I need to increase the sleep timing, the longer the recording?

Question: Is there an upper limit to the size of the recording?

As I am principally (at this stage) interested in bird calls, I have set the Audiomoth to filter on sounds in the range 1.5kHz to 12kHz (approx).

Question: Does this model (v 1.2.0) only record up to 24kHz and if so, how are people using it to record bats, which apart from Noctules, will be broadcasting at higher frequencies than this?

I will try with a shorter recording period this evening, but ideally I would rather have a series of files 30 mins or so in length to process in Audacity, rather that a lot of files 5 mins in length.

Thanks in advance for any help with this! :)