If my grandma is 94 and she does have good vision and hearing, does she still need take test for citizenship?

If she is eligible for a waiver, she can apply for that and see if it is granted.

As a matter of law, every applicant for naturalization must present him or herself for examination with respect to the application naturalization. There are exceptions and carve outs to this requirement. The most exceptions are those based on medical disability. If your grand mother has a physical or mental disability, she can seek and be granted exceptions based thereon. You did not provide a medical or any other basis for the exception.

If a doctor will certify that she will not be able to learn English or learn the civics questions due to a medical condition, she will be able to waive the citizenship test.

Yes, unless your grandmother has a medical condition that prevents her from studying for the test. A USCIS approved doctor must provide certification that she qualifies for the medical disability exception on form N-648.