one of the question interview ask for 1 of your strongest strength.
Should I just say that I am well trained to deal with customer service since I have extensive hands on dealing with irate users.
for weakness question: Should I say that I don't have weakness that might hinder my performance on the job? Is this a good answer?
I would NEVER answer the first question that way. It sounds like you're MAKING lots of pissed off customers, then having to correct those issues. Just leave off everthing after "since" and that answer is much better.
Weakness... always tough. I haven't found a good answer for that yet. I tend to just say that my one of my strengths is confidence, which can be mistaken for arrogance. Which is kinda-sorta true.
Probably the best thing is to get treated for depression. It takes a while, but can be done. Good luck, I know from first hand experience how debilitating it can be.