Grid builder requires a prefab to display as the grid cell if the mode is set to single cell or checkered. If in simple mode you will need to have a material on the grids mesh renderer.

If you are still not seeing anything cells, chances are you have autocellblock ticked, and the physics have not detected the ‘ground’. Please refer to this page on Setting up auto cell block.

The first step is to make sure everything is set up correctly. Please refer to this Quick setup guide on how to do so. This will ensure you have all the correct components to place objects such as the gridSquare, gridSelector and objectPlacer. If you are still not seeing objects placed, check out one of the demo scenes for scene setup.

Not at all. In fact, you set the object to be placed by calling the gridSelector.SetGameObjectToPlace() on the button. So as long as you call that method, it can be triggered by any scenario you wish.

Grid builder by default cannot place objects bigger than a single cell big. Grid builder 2 fully supports this feature and much more and is set to release in late April.

If you are comfortable with coding in C# then it is not too hard to implement this feature. See this post on placing objects that are larger than 1 cell.

Theoretically yes, but this is not a tested or ‘built-in’ feature. By adding a single cell grid to an object’s prefab and moving it just above the object you should get the result you are looking for. So when you place the object prefab, you are placing down another grid as well.