What I am trying to do is to create an elevated space inside the house. One of the areas has a corner that is unused, and I would like to put an indoor deck - something like this:

apologies for the partial photo - but hopefully it describes what am looking to do.
The size of the area is roughly L:250 W:180 H:241
My questions:
1) How do I go about it and plan for this? What sort of timber should I be after (I am thinking H4 - because this platform will sort of have a water feature (eg., water flowing over a Buddha statue)), being inside the house will be exposed to liquid spills etc. Is there a project page/link/video I could look at?
2) Instead of separated deck slats, is it possible to get a flat wooden finish (as seen in the photo) - what is such a thing called?
3) Because its indoors, what sort of shims should I consider for supporting the deck? Dont want the tiles/skirting to be damaged.
4) I am also planning to put some wall panelling to go with it. The wall is gyprock - am assuming most wall panel offerings can either be liquid nailed to the plasterboard or nailed into studs. When I search for such wall panels I only get results for sound proofing options - which end up being expensive for what I need. Any products I could look at which are just for aesthetics?
I am not quite sure if there is another way to describe what I am after - it feels right to call it an indoor deck.