$A$ liquid of mass $1 \ kg$ is filled in a flask as shown in the figure. The force exerted by the flask on the liquid is $(g = 10 \ m/s^2)$ [Neglect atmospheric pressure]:

Consider a mercury-filled tube as shown in the figure below. Which of the following options about the pressures at the lettered locations $(A, B, C, D)$ is true?

At every point of a liquid at rest,the tangential stress is zero. Explain with reason.

The density changes with pressure for which fluid? Give reason.

Three different liquids are filled in a $U$-tube as shown in the figure. Their densities are $\rho_1, \rho_2$ and $\rho_3$ respectively. From the figure, we may conclude that:

Two vessels have the same base area but different shapes. The first vessel takes twice the volume of water that the second vessel requires to fill up to a particular common height. Is the force exerted by the water on the base of the vessel the same in the two cases? If so,why do the vessels filled with water to that same height give different readings on a weighing scale?