Moved from Grasshoppers, Crickets, Katydids.

T. citrina (in Florida) has the lower rear angle of the sides of the pronotum projecting down somewhat into a rounded or toothed point, while on S. marmorata it is more nearly square (but broadly rounded) and doesn't project down. The pronotal crest on adult S. marmorata is higher than on T. maritima, but on nymphs the difference is much less, and from the top it's hard to see any difference at all. I may be able to tell which it is based on the sculpturing of the head or proportions of various body regions; I'll give it a shot as soon as I get a chance to compare photos. Sometimes the color pattern is a dead give-away, but this one is quite plain, and so there isn't much color pattern to go on.

Psinidia is a more distant relative, and different enough in structure at all ages that it is pretty easy to tell apart from these two. Other Sphragemon can be pretty similar too, but they have a higher more roof-like pronotum with a higher crest as nymphs.

I think this might actually be Trimerotropis maritima, but you might have it right - seeing the side would make it much easier to be certain.

As for gender, you can tell by the structures at the end of the abdome from the start (but it is much more difficult in the first two instars, and sometimes very hard to see in a photo). This one looks male to me, from what I can see. The male has the end of the abdomen basically capped with what is called the "subgenital plate" and so in most species it looks blunt on the end. The female has an ovipositor (egg laying apparatus) there, made up of four pointed hard "valves" that are held together and make the end of the abdomen look more pointed. There are often other differences as well, but females are generally larger, bulkier, and have proportionately longer abdomens and smaller heads. They are not sexually mature until after they become adults, but the characteristics are pretty much fully developed in last instar nymphs, with little change (externally) after that (so this one has pretty nearly fully developed gender characteristics already).

As for the wings, you are correct, this is a nearly mature nymph, and it will be an adult the next time it molts. Most species molt 5 times, and the stages between molts are called "instars", making this a last (probably 5th) instar nymph. The adults expand their wings right after the last molt while still soft, just like a butterfly does (just like all insects with fully developed wings do).

Moved from ID Request.