ds-2cd2032-i which firmware to download?

No need to update IP camera firmware unless you have a specific need or fix in mind. Just because it's newer doesn't make it a requirement. Beware that updating a Chinese region camera's firmware may well BRICK your Hikvision camera, and that would suck.
 
I was able to downgrade my Chinese cam to 5.2, converted it to English, and then upgraded to the latest firmware. I had 5.3, and the camera would stop working after a few hours. With the latest firmware, it works perfect.
 
How can you tell if my ip cam is Chinese? I have V5.1.6 build 140612 and it has English menu. Is it possible to upgrade and if yes which version do you recommend?