Hello Sameer
It is possible to purchase a model that has another IOS image and to upgrade that image with one that you may have. You just have to ensure that the image being used is compatible with the specific platform, and that you have the appropriate amount of memory required for it. By going to the Cisco Feature Navigator and searching by platform, you can see all of the compatible IOS versions, as well as their requirements as far as DRAM and Flash go:
You can’t break a device, even if you load the wrong IOS version. If it is not supported it will simply inform you in the CLI during bootup.
I hope this has been helpful!
Laz