Electrons are gained and lost.
Yes, most of the synthesis are redox reactions!
if u take an atom and smash it into another atom it will be known as a combination reaction, a reaction is considered 1. A combination reaction is considered more than 1.
2Mg + O2------> 2MgO
Yes it can. I believe that an example of such a reaction would be the addition of zinc to a solution of 6 molar hydrochloric acid (HCl).