OK, here is my attempt at making hard cider. Keep in mind I am not the expert here, so please watch with that in mind. This show has generated a lot of email….
You don’t mention it but did you use any campden tablets? They are used to kill any wild yeast that may be on the fruit at the time of picking. It’s pretty much guaranteed that there is wild yeast and bacteria on the fruit including the little bugs that make vinegar. This is probaly why your cider had a vinegar taste. Also if it was me, I would have added sugar to boost the abv (alcohol by volume) Just a few ideas.
try coring the apples first – we find when we make apple sauce that its the seeds & core that make it bitter. Nice color on the cider though, that’s why I’m thinking it was the seeds instead of it being vinegared … I would have thought it would have been more cloudy had it been vinegar. There are several recipes online for making home-made apple cider vinegar in a reused plastic bottle right on your own countertop.