Question [Q] Relock / Return to stock


I have a question about relocking bootloader / restoring back to stock.

I found out it was possible to relock bootloader using Flashtool. If I flash a stock Sony ROM using Emma, and then relock the bootloader with Flashtool, does it mean I will be back to factory state ? Will I be able to do OTA updates etc. ?

Or is there no way back ?
I did not save the TA partition before unlocking...