When I submitted my app to the Mac App Store, it displays something like this to users:
and it won't allow anybody with an earlier version to download the app.
I see there's a LSMinimumSystemVersion key in my app's Info.plist which is set to ${MACOSX_DEPLOYMENT_TARGET}.
If I want to let users with an earlier version than 10.7 to use my app, can I then just change the Deployment target? Will my app then run on versions earlier than 10.7 (I will be building the app on 10.7)?
Another question, can I make the change without having to wait for Apple to approve the binary again (I just want to change the minimum Mac OS X required version, not anything in the binary itself)?
Provided your binary supports it of course you can at least set the minimum system requirement to 10.6.6 (when the MAS came out) - and probably 10.6 if you wish.
There is no explicit rule that I know disallowing, say 10.5, but there is one forbidding "deprecated technologies" and this lists Rosetta which would undoubtedly be interpreted as no PowerPC binaries.
It's a change to your binary, it will have to be approved. Put a note in the comments to reviewers section stating that is all you've changed, can't hurt, may help.