1) What are the differencers between troubleshoot and pinpoint?
You troubleshoot something that has a fault.
If you pinpoint something, you are identifying it in isolation from anything else.
I need to troubleshoot my computer to find the problem. Ok now I've found the problem I need to pinpoint the cause so that I can fix it.
2) What are the differences between these: Interpool, FBI, CIA,SWAT?
I can't answer in any detail other than to say Interpol is a European based agency, the others are American.
3) Is trash a countable noun? -- No