Best combination of versions of MacOSX / LC / Xcode ?

[livecode_]

<span style="font-family:arial,helvetica,sans-serif; font-size:12px">‌Hello everybody,<br>
I am brand new to this list although I have been using Metacard / Revolution in the past.<br>
I presently have the project of developing an app that would run on iOS and Android<br>
mobile devices, and was wondering what is the best combination of versions of<br>
MacOSX / LC / Xcode for such a project ?<br>
Thanks in advance.<br>
<br>
M. Leraille</span>