Thanks aaronpang for your very helpful tips. I used them when I made my 2nd inspection last week.

Today I learnt something new too. Just to share if it hasn't already been. Use a 50 cent coin and knock the wall tiles to find hollow ones. The result:



But when I knocked the floor tiles with a piece of wood, the sounds sound pretty much the same. Not good at this!

And then I flooded the bathrooms. The result:

Water stain in the living room beneath the master bedroom:



You can even see water dripping from the cracks (plus water stains) outside the house, above the electric meter!




Note: A construction contractor told me that all bathroom tiles were not fixed with water glue (or something like that, thus it is not surprising that this happened)

Question: What would the developer actually do with all these problematic and hollow tiles? Will they actually do anything?
They might say, you aren't supposed to flood your bathroom or hurl things at the wall anyway