Can Lino be laid directly on top the top of caber boards?

No id hardboard ontop first

Yes, but depends on what kind of glue used.

No you'd have to ply it first and the ply would be stuck down then obviously feathered before fitting the vinyl. Hope this helps

A vinyl will only ever reflect the floor that is underneath and as such you'd want at least a hardboard down. Best practise is to put a good 6mm flooring grade ply down first, if in a bathroom, a marine ply but at a very minimum - hardboard would be required in my opinion.

I have recently fitted vinyl on four apartments directly onto caber boards , as long as they are perfectly flat no raised joints it should be fine