Whenever you're ready! The lessons are available online any time, and your access to the class never expires.
As long as you need! Your access never expires, so you can come back again and again.
Ask your questions on the platform and you'll receive instructor feedback. Your fellow students are also likely to jump in and offer advice from their experiences.
Kirsten is a big fan of available light, so you will learn a lot about how to gauge and compose for the light you are seeing. Kirsten does not give direction on using a flash or off-camera speedlights.