Usually it has been possible to open a later version in an
earlier version by using the HHP file. As Kathy says, X5 will not
recognise the new features but in the past it could always be a
safety net as long as you avoided those features.
Curiosity made me try do that with a RH7 project into X5. I
found that when you click File | Exit or the Windows X button, X5
crashes.
There are additional files created for RH7. In time it may be
possible to track down what causes the crash but that's for another
day. It looks like the only way back would be to import topics back
into X5 My quick test suggests that if those topics contain some of
the code for the new features, that too could cause X5 to crash.
So until someone has the time to dig deeper, make sure you
back up the X5 project. That said, do remember we are just talking
about IF you have to go back. Check your upgraded project before
going on to far and you should be OK.
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