How to open the back cover of this device?

I am unable to open the back cover of HTC D630. In the process of doing so, I damaged the back cover, and broke the screen. I had taken it to a repair shop. They could use some help.

I had exposed it to rain, and it was not turning on the next morning, so I thought, I could take a look. Turned out, it just needed some charging. I had tried a slot metal screwdriver on it.

Device bought in India.