What does an electric dipole experience when placed in a non-uniform electric field?

Charges are placed at the vertices of an equilateral triangle as shown in the figure. What is the resultant dipole moment?

For the shown situation of two dipoles,the nature of forces between them is:

$A$ small electric dipole $\vec{p}_0$,having a moment of inertia $I$ about its center,is kept at a distance $r$ from the center of a spherical shell of radius $R$. The surface charge density $\sigma$ is uniformly distributed on the spherical shell. The dipole is initially oriented at a small angle $\theta$ as shown in the figure. While staying at a distance $r$,the dipole is free to rotate about its center. If released from rest,then which of the following statement$(s)$ is (are) correct? [$\varepsilon_0$ is the permittivity of free space.]
$(A)$ The dipole will undergo small oscillations at any finite value of $r$.
$(B)$ The dipole will undergo small oscillations at any finite value of $r > R$.
$(C)$ The dipole will undergo small oscillations with an angular frequency of $\sqrt{\frac{\sigma p_0}{4 \varepsilon_0 I}}$ at $r = 2R$.
$(D)$ The dipole will undergo small oscillations with an angular frequency of $\sqrt{\frac{\sigma p_0}{100 \varepsilon_0 I}}$ at $r = 10R$.

$A$ system has two charges $q_{A} = 2.5 \times 10^{-7} \; C$ and $q_{B} = -2.5 \times 10^{-7} \; C$ located at points $A: (0, 0, -15 \; cm)$ and $B: (0, 0, +15 \; cm)$,respectively. What are the total charge and electric dipole moment of the system?

Two charges $+q$ and $-q$ are kept at a certain distance apart. Then, at any point on the perpendicular bisector of the line joining the two charges: