Domestic Conduit / Cabling Questions

[Citroënbender]

Referring to this simple diagram, not to scale. Meter box is the lower right:

I’m still waiting for the sparky to come!

These new circuits are spec’d as 6mm, 32A. While I’m waiting either for old mate or someone else more motivated, thought I’d run conduit and pull cables so the job is reduced to checking and termination.

Q1: Do circuits of this amperage require conduit along their entire length - or only when breaching an exterior wall, running underground or otherwise exposed/unprotected?

Q2: The longer run, I have the options of either ceiling cavity (thence wall drop) or subfloor routing, which is recommended? I know that ceilings typically carry more fire risk and cabling is sometimes derated in them.

Q3: Subfloor - the short leg - do I have to follow the run of bearers and joists, or can I take the most direct route (as sketched)? I realise this situation / possibility is impacted by any conduit requirements.