The plant in the middle is small but healthy basil. It is in flower, but it is not flowering very profusely. This is not a problem. The leaves are edible at any time. The flowers are edible at any time.

You can collect the seed by putting a little bag made of thin fabric (like pantyhose material) over the flowerhead and securing it on. The fabric must allow the light in, and the water out, and the attachment to the stem must not be tight enough to squeeze the life out of the stem. It's just a matter then of waiting. When the seeds are ripe, they'll fall into the bag. To collect, snip off the slower stem, turn the bag upside down and open it from the top. Not all the seeds will have dropped in, but they're easy to collect if they're ripe. There will be one inside each little flower, and it's more likely to be ripe if the flower is well and truly dead and dried out.