Do I need to update...

Cubase
1

I just upgraded to C11. I’m wondering if I need to update the other components?

Halion Sonic SE
Groove Agent

Do I need Spectral Layers ‘One’ if I already own the full SL?

2

Halion Sonic SE and Groove Agent:
Instruments: yes, the programs are updated.
Content: no, the content is the same.

SL One: no, you have the full version.