I have an image that is currently cmyk colours. It has also been flattened.
How do i convert the colour profile to spot colour for the printer?
You don’t seem to understand the terminology.
What print process: offset, gravure, flexo, …?
And as for the opacity that depends in part on the process and you best ask your printer about it.
If the colours are opaque one may not have to knock out the red under the dark blue, if the colours are translucent one may have to.
All about creating and assigning spot channels: