Surely ply has better moisture resistance.
Can hardboard be place on top of vinyl tiles.
If your flooring is already thick enough needs to be stable to prevent cracking later.
Stir ready to use floor patching compound with a paint stirring stick.
4 loose lay more boards up down and across the room.
I believe you want to be tiling on something like cement board or ditra not directly over plywood.
It can be confusing because many leveling compounds are marked as useable on a variety of surfaces including linoleum and vinyl.
3 adjust it so that the edges do not correspond with the gaps between the floorboards.
If you are planning to tile over the hardboard make sure that the rough mesh side is facing up to give more of a key for the tile adhesive.
Fill low spots on the floor with patching compound applied with a putty knife.
2 loose lay the first board over the centre with its long edges at 90 degrees to the floorboards.
Two layers of 5 8 plywood at least then use cement board.
It is not a good idea to lay ceramic or stone tiles on suspended upper floors unless you are sure that the joists can carry the extra weight consult a structural engineer for this.
How to 4 laying hardboard and plywood 1 use a chalk line to mark two lines at 90 degree angles to each other across the centre of the room f2.