It is important to understand that volume recommendations are highly individual - one person might thrive on, say, 20 sets a week of an exercise while another could be destroyed by this level of activity. One person might need a minimum of 5 sets a week to progress while another would require at least 10 sets. An individual’s athletic background, current training history and genetic predisposition contribute to this.
That said, beginners will generally require lower volume, less stimulation, in order to cause a change in their bodies. Beginners should be careful with doing too much, as they have not yet built up the work capacity (how much you can do in a session) and recovery ability (how quickly and effectively you heal between sessions) that more advanced athletes have.
For beginners with an athletic or weightlifting background of any sort, progress will come fast and there will be an initial period of quick strength and muscle gains (assuming the calisthenics movements require new muscle that has not previously been built) due to the new movements.
Still, this group should be careful with too much calisthenics volume, as the joints and tendons will need to catch up to the rest of the body.
In terms of workout length and frequency, first and foremost the workout schedule must fit the individual’s life. If you only have 20 mins 4 times a week, then we start there. Forcing a 2 hours, 2 times a week plan into this is impossible. Consistency and adherence to a workout plan is by far the most important.
Assuming no time constraints, a complete beginner could start with a 1 day on/1 day off or 1 day on/2 days off workout schedule. This allows the athlete to gradually get used to the workload. Ideally, over time the 1 day on/2 days off group would move to 1 day on /1 day off or a Mon/Wed/Fri/Mon schedule or similar.
Once acclimated, there should be no problem with training daily.
In terms of workout length, excluding the extreme options such as <10 mins or over 3 hours, there are no hard rules here. You may have heard of the ‘don’t exercise more than 1 hour’ myth which is based on an exaggeration of the effects of cortisol. Unless you are thrashing your body hard 5 hours a day non-stop for weeks, this won’t affect you.
In the beginning, you will either only be able to exercise for a short time or you will take longer to do a certain amount of work. As you become more advanced, you will have the stamina and capacity to exercise harder for longer. You will also be able to do more work in less time with less rest. However the exercises also get more difficult, which then requires more time and rest.
Ultimately, it’s important not to stress the details as a beginner. Find a comfortable starting point in terms of number of workouts per week and length of workout, stay consistent and gradually build from there.