>>AFAIK, the most important module of .net, the CLR, is only available and supported on devices running Windows, in other words Windows computers and Windows smartphones. There appearantly is a CLR version available for Apple and possibly also one for Unix, but they are more or less dust collecting open source projects with minimal or no support.
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>So, if a corporate policy is towards .NET, for the front end development, based on your knowledge, it would be practically impossible to develop apps for smartphones. Is that correct?

You will be limited by the CLR versions available for the different smartphone OS's. In practice this means that have a limited range of available functions since the CLR versions for smartphones other than those running Windows, are relatively old.