Is it possible to install ios 6.1.2 on iphone 5s?

If i found the ios 6.1.2 data, could i do it?

Wow it's nice question.
i really like it

Your question is way too vague.

What version of iOS are you currently running? And, what version of iOS was Factory PRE-installed? And, this is important, WHY do you think that you need to be running iOS 6.1.2, anyway?

Give us something concrete to work with, and we'll try to help you further.