Background check for operations - How bad is this??

Hi, been a lurker for a long time but I have a question about the background check process at investment banks.

I was offered an role in operations at a bank that I'd really like, but I'm wondering what exactly they're looking for in the background check as I'm filling out the forms now.

When I was younger (5 years or so), I fell on some hard times and had a bit of trouble paying bills. To help deal with the electric, phone, etc. bills that were coming up, I would put as much of the other stuff on credit cards. In the end I couldn't pay off the cards and they went delinquent and they ultimately canceled my cards, so my credit wasn't the best and part of the background check involves a credit check.

Long story short, I got 10 years for armed robbery and assault with a deadly weapon. I managed to get the sentence reduced to 5 years though due to good behavior, and after a long job search I finally got this opportunity I really want.

So I'm wondering:

1. Is the credit check going to prevent me from getting the job? Do they care more about the credit or the criminal stuff or is it both?

2. How much do you think the criminal charges would hurt me? Is there any difference between FO and BO in terms of how much they'll look past that?

3. Do you think if they see I got the sentence reduced because of good behavior, that would help?

4. They ask for an explanation on why I have the conviction. What should I put in that space? Is it something where they want a sentence or two or am I supposed to type pages of detail in there?

Anyone whose gone through the process and can help would be much appreciated. Thanks