07-09-2015 04:37 AM
each version of FOS release notes contains this information. so you need to decide which version will be the highest in your setup at the moment, e.g. 7.2.1e. then you need to have a look at 7.2.1e release notes - it will tell wich version is the lowest compatible with 7.2.1e. that's it.
other sections that are good to review - known and fixed defects.