Electric field due to a short dipole at a point $A$ on the axis

1. There is a short dipole $X,Y$ of charge $+q$ and $-q$ placed along the x-axis and then we consider the point at $A$ which is far away from the dipole and lies on the x-axis. The electric field $E_\text{net}$ experienced at that point will be $E_\text{net}=E_\text{XA}+E_\text{YA}$ where the $E_{ij}$ are vectors. The dipole charges also interact with each other. Why are we only considering the interaction between the dipole and the unit postive test charge at the point $A$?

2. Would it be the same if we did the following? Keep a positive charge $+q$ at the origin and another positive charge at a distance far away on the x-axis. After that, introduce a negative charge $-q$ near to the origin. Will this result in the same configuration (in terms of electric fields) as in the previous case?