You can use
Context("Numeric"); Parser::Number::NoDecimals; ANS(Compute("$c/2 pi")->cmp);
to get the effect of your first example using MathObjects. Note that your flags do not prevent students from entering decimals or functions. They only affect how the student and correct answers are displayed.
If you want to disable functions so that students have to write
1/2 rather than
sin(pi/6), then you can use
There are other categories that can be disabled, or you can disable individual functions. See the Wiki page on Answer Checkers and the Context for details.