particle physics - More on matter and anti-matter

1. 
   

   Does every particle that has rest mass also have an anti-particle with which it would annihilate?

   
   


2. 
   

   Does annihilation only occur between like particles? For example what happens if a antineutron (anti u, anti d, anti d) collides with a proton (uud)? What happens if a positron collides with a proton?

   
   



3. 
   

   Since the Tevatron accelerates antiprotons is this more difficult to handle and dump?

   
   


4. 
   

   I've read about WIMP annihilation detection. Why would one assume there is any different proportion of WIMPS to anti-WIMPS than as is for non-WIMP matter (where there is far more matter than anti-matter).