Yes, you are correct, your NI-DAQ C API programs for E-series boards will NOT be backwards compatible with Lab-series boards like the 1200. We know this is a major inconvenience with our DAQ API in C, but was originally unavoidable with the vast differences in the architecture of these boards. We are working on resolving this problem by creating more consistency in the NI-DAQ API.
As for your second question, your aren't actually losing resolution if you are properly gaining your signals. You can set the gain with AI_Setup. If you want to use an input range for your signals of 0-10V, then set your gain to 2. If you want a range of -1 to 1V then set your gain to 10. You can find the valid gain settings for your board in the AI_Setup help in the NI-
DAQ Help.
Best Regards,
Chris Matthews
National Instruments