How often can I spray my flowers and veggies. Once a week, month, etc.

if you're talking about just for fertilization, I would say every 2-4 weeks. If it's to take care of a pest problem, probably every 2 weeks.

It all depends on what you are doing.
As mentioned, if your only purpose is to just fertilize plants, then waiting several weeks between usage is recommended.

However, if you want to continuous feed the beneficial aerobic soil/composting microbes in your topsoil and on your plants, for better plant health, plant protection, and soil building, then there are unlimited ways to do that without harming or overfeeding plants.

If you create a very, very, weak and dilute plain compost tea or molasses tea, and use it only as a soil drench, you can actually use it as an irrigation substitute for your plants weekly!

Happy Gardening!