Yuppers. What you have there with a baby cucumber attached to the base of the flower is the FEMALE cucumber flower. These are the ones that, when pollinated, will grow into cucumber fruits. The flowers you have been seeing on the cucumber plants, that had NO baby cukes attached were the MALE flowers. Their sole function is to produce pollen and have them transported to the female blossoms to pollinate them. usually they are open for one day only.
Wasps and flies, ants, even hummingbirds can also transfer pollen to the female blossoms. Easiest way to do this yourself is to pluck a male blossom and have it "kiss" -- face-to-face -- a female blossom.
The tomatoes are looking good! Those flowers are self pollinating. The cone shaped yellow part is called "anther cone" and produce pollen inside. Wind or bee buzzing on the blossom causes the pollen to be released and "snows" over the female part of the blossom inside or just protruding from the cone (usually inside). You can simulate the bees by touching the arching stem of the blossoms with an electric toothbrush. It is kind of fun because you will actually see pollen come right out of the anther cone. Same thing can be done with peppers and eggplants.
But I see in your windowbox, spinach, basil, and what looks like corn seedlings?
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