lyx2.3.0beta1 lyx-file export not taken by lyx2.2.3

[Wolfgang Engelmann]

Is it true, that a lyx-file produced by lyx2.3.0beta1 is not taken by 
lyx2.2.3?

and, if so, which lyx2lyx shown in lyx-2.3.0beta1/*lib/lyx2lyx* should 
be used for conversion:

lyx_2_3.py

           .pyc

LyX.py

      .pyc

lyx2lyx

lyx2lyx_version.pyc

and how?

Wolfgang