toppling of object

Both are correct.

Whether the block will topple or not, it depends on 2 factor.
1.The amount of Force you push.
2.The postition you push.

In Form 5, we do not have the knowledge about the moment, so we do not consider the
postition of the force added on the block. So you will have a diagram as you have drawn.
There is a hidden assumption in F.5, the block is a point object, the "block" is just a point.

In form 6, we learned moment. Since the block is 3D, we treat it as block not point, which
have size.Force acting on different position, will cause different effect.If the force is large
enough and acted on a postion much far away from the C.G. The block will be topple off.

So Both are correct, as F.5 has an auumption, while F.6 do not, so it seems to be having
two answer.

Hope that can solve your problem.
:)

Both are correct.

If friction is high enough, then a force applied to the object above its centre of mass may topple it over. Otherwise, the object will move forward.