The first type requires an allen key. It has a recessed hexagonal head to undo. Its advantage is supposed to be that it will not be caused to come undone by things touching it.
The last one needs something to turn the pin using the handle (the exposed flat with a hole through), and that might be fingers, for finger tight, or that shackle key, by putting the tapered slot over the flattened pin handle and turning.
Most shackle applications require more that finger tight. In some cases (such as anchors) locktite fluid is a great way to prevent unintended loosening.
Geoff.
"Contender" Rival 32: Roseneath in winter, Mooring off Gourock in summer.