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Hi Juan,

AutoCAD 2018 for Mac is not available, but you can join Beta testing here:

https://forums.autodesk.com/t5/autocad-for-mac-forum/want-to-view-the-pre-release-version-of-autocad...

And - yes, you can open drawing created in AutoCAD 2017 for Mac in 2018 version of AutoCAD for Windows without any troubles.

Maxim