How does pressure due to a liquid held in a container vary with :

(a) Depth
(b) Shape and size of the container.

When a liquid is enclosed in a container, 

(a) As depth increases, pressure exerted by the liquid also increases.

(b) Pressure of a liquid is independent of the shape and size of the container. 

When pressure is exerted on an object from opposite sides in opposite directions, the two forces either get cancelled if they are equal in magnitude or the force that is more in magnitude comes in play.
The object gets pulled to that side where the magnitude of force is greater. 

The foundation of a building is made wide so that it do not dug deep under the ground during extremely high pressure generated by the weight of the building.

As, Pressure = $\frac{\mathrm{Force}}{\mathrm{Area}}$

The broad foundation distributes the weight of the building over a larger area and keeps the building safe from falling. 

Cutting instruments like  blades and axes are sharpened to decrease the area of cross-section that is in contact with the object being cut.

Using the formula,

Pressure = Force /Area, we can say that with decrease in area the pressure exerted by them on the surface increases. Thus, they can easily penetrate the surface that they are meant to cut without applying much force. 

Pressure is given by force per unit area. 

The pressure exerted by the sharp knife edge is more than that exerted by the blunt one since the area in contact for the sharp knife is smaller than the blunt one.

Thus, it is easier to cut with a sharp knife than with a blunt one.