gnt build on win 2012 and deployed on win 2016

For the Windows product, the OS version on which a program was compiled has no bearing on the OS on which the .gnt is deployed as long as both of these OS versions are currently supported by the product version that you are using and that the COBOL Server product is at the same version level or higher than the Visual COBOL compiler that was used to generate the code. There may be additional environmental concerns such as security, firewalls, etc that may have to be addressed but the .gnt module itself should be compatible between the two supported platforms.

To check if a particular product release is compatible with an OS version you should search the Product Availability Matrix which can be found on the Supportline site here.