Question

What are the quantum reasons due to which attractions and repulsions happen between like and unlike charges

Answer 1

Attraction and repulsion itself is a quantum phenomenon.

The "quantum" reason for that is essentially "stability".

Every thing in this world wants to be stable.
Water flows, earth spins, chemical reaction occurs, are all examples of steps that lead to stability.

The most stable particle will be a neutral one with inter or intra molecular or atomic forces.

A charged particle is greatly unstable. It has a unstabilised quantum field, which requires something to be stable again. That something is what we call an opposite charge.
When charged, a particle has disoriented field. This field interact with other particles and their fields, which destabilize the particle.

So, basic drive is stability in all manners. Atoms need octet, particles need neutrality.