These guys will mate in freshwater but the young need salty water. I dunno the salinity though. You can search around for more information on that.
Their young are actually little plankton rather than small adults like RCS. More like a ghost shrimp, just harder to raise and requiring salt.
Now I've heard some people leaving their pregnant amano shrimp and claim to find a small amano shrimp surviving. Now these are rare cases and may be misinformation/stories or just those rare cases.