can i upgrade my 3gs to a version 6.1.6 from 6.1.3?
iPhone 3GS, iOS 6.1.3
Yes, iOS 6.1.6 was released to upgrade the security in those iPhones that could not upgrade to iOS 7.1.2. Tap Settings > General > Software Update and see if it doesn't tell you that you can update to iOS 6.1.6.
but does it affect its performance? its 16GB
No, updating from 6.1.3 to 6.1.6 should not affect performance...all that does is patch a security issue.
Can i upgrade my 3gs to ios 7?
if not how can i downgrade ios 6.1.6 to 6.1.3?
The iPhone 3GS cannot go higher than iOS 6.1.6. As with any other iOS, Apple does not support downgrading to a lower version. Once upgraded you cannot go back.
can i upgrade my 3gs to a version 6.1.6 from 6.1.3?
