Thank you for your reply AgitatedDove14 !
For the point 1, here is what is printed out when the task starts execution for the first timeSyncing scheduler Failed deserializing configuration: the JSON object must be str, bytes or bytearray, not NoneTypeHowever, now I see that this actually doesn't break the code, and this exception is ignored. The task is not started in the first run, but this is because of the reasons discussed in the point 3, I assume. Sorry for a false alarm here.
For the point 2, I was thinking of a use case where we have a heavy job to run, which we would like to schedule for a night time on a Saturday, for example, when the server load is low. Or can this be achieved by e.g. scheduling a job for weekday=saturday, hour=3 ? For the point 3, yes, I think we would expect the execution immediately. For example, if we want a job to run every 15 min, we don't want to wait 15 minutes for the first execution to happen, we want to start straight away, and then repeat every 15 min 🙂