hacking:
Unauthorized use, or attempts to circumvent or bypass the security mechanisms of an information system or network.
reversing:
Reverse engineering (RE) is the process of taking something (a device, an electrical component, a software program, etc.) apart and analyzing its workings in detail, usually with the intention to construct a new device or program that does the same thing without actually copying anything from the original. The verb form is to reverse-engineer, spelled with a hyphen.
When you have fully reverse engineered a piece of software then you completely understand how it works. That doesn't mean you also 'hacked' that piece of software. Does installing a hacked drive makes you a hacker? No ofcourse not, that's just plain silly. You didn't circumvent any security mechanisms, the original author of the firmware hack did.