It will flower with light cycles of 12 hours on / 12 hours off. When to flower is up to you. It will generally triple in size during flowering.

The larger the plant, the more light it will need.

Many things you need to consider here. Best advice would be to let it veg (16 hours of light per day or more) for another month, maybe 2 months. A plant will show that it is mature and ready for flowering when you see pre-flowers (you can find examples of pre-flowers with a simple google search).

You can also flower before this, but your yield will not be as much (the longer you veg, the bigger the plant, the more yield). However, without enough lighting, vegging for longer will not give you dense, thick, high-yielding buds.

Have you thought about outdoor growing?