Easy answer is yes but you will need root for 4EXT as it needs Superuser permissions to run, don't have to be s-off. I'm not sure how to do it without root but I'm guessing there may be a way using terminal commands on your pc. Try searching the permanent links at the top of this forum or the XDA thread as well.
You can also backup your apps separately to restore their data later but using on of the many PlayStore apps for doing so like MyBackup Pro or Titanium Backup (my app of choice). Good luc
*Edit (above) hah, posted while I was posting mine. Looks like we agree full locked can't be done, Helium looks nice too.