I have blue cross blue shield insurence does it cover gastric bypass if I want to have it done?

Maybe. You will first have to choose your surgeon and have a consultation. If you meet the criteria, it maybe covered but you will have to follow through on the prescribed program. It can take a few months to know. Just calling the company may not work. The surgeon will be able to tell you.
It depends. You need to call them directly. Different plans within the same company may have dramatically different coverages for bariatric procedures.
Possibly Yes. It depends on two things: 1) the benefits spelled out in your insurance plan contract, and 2) the medical necessity criteria your health plan has adopted when this surgery is a covered benefit. If this surgery is an exclusion, it's unlikely your health plan will cover it. Best way to find out is to call the customer service number on your insurance card or ask your doctor to find out for you.