Jet has the J herringbone BOM-LHR and back. However from SIN to BOM they used to use 737 s which have a old skool J seat. I ve recently heard they fly the A330 s on which they have the herringbone. So you d have the herringbone !

As far as flying Y goes sorry I havent flown it on jet but the inflight service is usually good ( they make a good effort on international sectors ). Your seat will have a screen aswell......