Yes, damsons are scrumptious. They make good jam and chutney if you have the patience to take out the stones first - they float on the top of the jam so scoop them off. You can cut them out of the fruit first but it's tedious and it stains your fingers black! Any damson I plant here tends to do well for a couple of years then gets a disease and we have no more fruit
Damsons are a deep blue/purple usually, with a soft bloom to the skin.
I've never tasted sloes and I don't drink gin - which are irrelevant as I don't have any here.
Sometimes plums revert or die back to their rootstock which could be what your shiny black fruit is. Sheep love all kinds of plums but make sure they spit out the stones, otherwise they can block a stomach, like acorns do. I suppose you could check their droppings to make sure any which are not spat out pass right through
The last fruit looks to be the wrong shape for a Victoria because of the pointed bottom, but let it ripen and see how it turns out.
I grew up in Norfolk where we had all sorts of tree fruit and a large area of reverted plums - we called them bullaces but they weren't in fact. I really miss the ease with which everything grew back there - now I live in Scotland and every single food crop is a hard slog to grow - except potatoes