Should any pruning be Done once Flowering Begins??
Good question. I assume you are growing cannabis.
It depends on what strain you are growing and how your plant is shaped. It if is a small autoflowering plant, you shouldn't need to. If it's a big and bushy photosensitive plant that doesn't seem to stop growing new leaves, you may want to. In either cases, you can always pluck one or a couple leaves, but it's a bit different with a heavy defoliation as it is a lot more stressful for the plant. It also depends on what light source you have and its light footprint. If all leaves are illuminated, there's no need to pick any leaves. It's also a possibility to bend and tuck any leaves creating shade, to expose bottom leaves to more light.
Some growers prefer defoliating heavily and pick the fan leaves in early flowering, and some only take a few leaves. Some growers prefer to not defoliate at all and instead focus on low-stress training. It's personal preference. If you have more than one plant, try it on one of them and compare the results. See what option fits you and your setup best.