The first horse doesnt really appear over at the knee, more like he stands under himself quite a bit. Also his hind legs arent severely sickle-hocked. He's more camped out than anything
As for the 2nd, that one IS sickle-hocked so I would say no for jumping.
The last one you posted is not bad compared to the others, though he/she needs muscling and the neck is a tad long. Overall, the build is not perfect but the best of the 3 with nice hindquarters and relatively sound-looking legs