Flashtool 0.9.18.6

: For Xperia Z series and older, stick with 0.9.18.6. For Xperia X, XZ, 1, 5, 10 series, use Flashtool 0.9.30+.

Unlocking the bootloader allows custom kernels and full root access but wipes DRM keys (back them up first!). flashtool 0.9.18.6

If you are strictly upgrading and want to keep your data, leave them unchecked (though a clean wipe is always recommended to prevent post-flash bugs). : For Xperia Z series and older, stick with 0

: Users attempting to root Xperia Z1 devices (model C6903) running Android 5.0.2 (build 14.5.A.0.270) with Flashtool 0.9.18.6 reported failed rooting attempts, even after searching extensively for solutions. stick with 0.9.18.6. For Xperia X