Is it possible to save a project in ArchiCAD 27 compatible with 21?

[eakhd]

I use AC 27 while my colleague uses 21. He wants to see my project while I am on holiday. Is it possible to save my file as 21? Or is there any other way for him to be able to see it?

My search on Google didn't provide much insight. I know that 27 can save to 26. Does that mean that older versions are totally incompatible with 27?

Thank you for any replies.

[Lee Hankins]

You can back save to Archicad 21 but you will need to save backwards version by version so from 27, backsave to 26 and then open in 26 and backsave to 25 and so on. However, any elements or settings that specifically relate to new features in each version will be lost as you save backwards. Going from 27 back to 21 will likely lose a lot of functionality and features and potential data.