Do the swimmers that swim prelims in Olympic relay (and allow team a place in finals) but don't swim the final race receive any recognition?
They get medals, but they don't get to stand on the podium. Most of them just go for the experience, so that they can be medal contenders in the future. They also are allowed to attend any victory ceremonies that their country may have.
Yes, they get medals if they competed in prelims. What interesting is that coaches for team events don't receive medals. Some think that at least 1 coach should receive a medal for all team competitions at the Games!