A capacitor is connected to a battery. Once the capacitor is fully charged, how much energy is stored?

Consider the circuit:

If the voltage drop across C2 is 5V, what is the total energy stored in C2 and C3?

If , and , how much energy is stored in ?

You have 4 capacitors, , , , and , arranged as shown in the diagram below.

Their capacitances are as follows:

If you have a 6V battery connected to the circuit, what's the total energy stored in the capacitors?

Imagine a capacitor with a magnitude of charge Q on either plate. This capacitor has area A, separation distance D, and is not connected to a battery. If some external agent pulls the capacitor apart such that D doubles, did the internal energy, U, stored in the capacitor increase, decrease or stay the same?

Imagine a capacitor with a magnitude of charge Q on either plate. This capacitor has area A, separation distance D, and is connected to a battery of voltage V. If some external agent pulls the capacitor apart such that D doubles, did the internal energy, U, stored in the capacitor increase, decrease or stay the same?