Dear friends i have cubase 9 pro with Halion Sonic SE2 .I have also download Halion Sonic SE3.(is this update??)Can i install this version or this is not necessary.Wait for your answer.Thanks.
Yes, you can install this update.
Note that Cubase 9.5 already comes with Halion Sonic SE 3.
Exclusive to Cubase 9.5 is the new Flux wavetable synthesizer for Halion Sonic SE.