Excess of matter over antimatter.

Familiar with the question of: "where is the missing antimatter"?
I have more than one scenario to answer it:

1. The amounts were never equal
2. The amounts were initially equal, but:
   2.1. Black holes swallowed them asymmetrically, because what are the chances of exact symmetric swallowing?
   2.2. They began equal, and remained equal, because the supposedly missing antimatter may reside in remote areas of the observable universe, or beyond its events horizon.
   2.3. combination of 2.1. & 2.2.
3. Can matter turn into antimatter or vice-versa?
   Can not it be done in Feynman diagrams?