De facto there is an age requirement, it is about 12-13 years old at the time of submission. It is not easy to overcome this requirement, but it is very rare when a person has high school education or equivalent by that age. 16-18 is well above that requirement.The High School Education requirement pretty much eliminates anyone under 17 since the vast majority of people graduate at 17 or 18, with most at 18. That requirement is just to apply and get to the interview stage if you get selected. If you apply at 17, and get selected, by the time you get to the interview many, many months later, you will be 18 or close to 19 and either in post-secondary education or working so not exactly a naïve, lost little babe in the woods. At the interview, they'll look at the things that you are confused about - whether the young selectee can make it on their own. There's a lot of discretion used by the CO. I'm sure they'd look at a number of other factors so as to make sure the young selectee won't end up destitute.
If this issue was a big concern or problem, I'm sure they'd have changed the requirements by now and increased the minimum age but I don't believe there's been a minimum age requirement since the DV was instigated (I could be wrong).
You need to have high school education or equivalent or work requirement by the time you submit I-485 or DS-230 form, not necessarily by the time of submitting an electronic entry..