How do you sync developments to a live site?
So a few things, if you turn on logging then you'll get a full timestamped history of changes to all tables in the database. If you had this on both environments then you would now be able to see all the changes.

However what your describing is a workflow issue, i.e. having changes happening in two environments without being clear on how changes will be released from Dev -> Prod seems like an oversight and not one CiviCRM will solve (Sorry - not trying to be rude).

In our pre-prod implementations we always define where customers are doing their prod configurations, where we're doing our dev and which environment is for playing. This way we have a clear release process from Dev -> Prod. We also introduce staging environments at the right time.

Hope that helps!