Rigidbody: how to get collisions for the current frame ?

I am trying to make a character controller using a rigidbody, for a sidescroller. The problem is in detecting the collisions. I need a way to get similar result to the character controller unity provides( when it collides on the sides, on top or bottom).

My question: Is there a way to get a list of the colliders my rigidbody is in contact with at the current frame, WITHOUT keeping track of the OnCollisionEnter and OnCollisionStay events ?

If not, how reliable are these events? I am developing for mobile platforms. Is there a possibility that an OncollisionEnter event won't trigger, and get an OnCollisionStay without it?

Also, during a physics frame, what gets calculated first, fixedUpdate or collisions( OnCollision events )?

Thank you for your time, Claudiu