Calculator special function Forms

I am trying to make a calculator function with a form.  However I am finding the documentation to do this lacking and have some questions about setting up the form and about setting the buffer.

The example provided uses a function "ahiCreateStringField" which is otherwise undocumented.  It seems to act exactly the same as "hiCreateStringField" (no "a" at the start")  However when I define a field using a function without the a and one using the function with the a in the same calculator form it doesn't display the form when you click on the function in the calculator.  I also noticed that I seem to be able to add other types of fields by taking a normal form function and appending "a" on the front.  However none of theses other functions are mentioned at all in the documentation.  

Form Questions

1. What is the functional difference between "ahiCreateStringField" and "hiCreateStringField"?

2. Do all of the form functions have an "a" equivalent?  Is there a way to check what arguments they accept?

Buffer Questions

3. Currently I am using "calCreateSpecialFunctionsForm"  to set the calculator buffer.  However this automatically puts the current buffer value as the first argument to my function. It seems like I could write my own CB function using "calSetBuffer" to set the buffer,  Is there anything else I need to take care of when I do this? 

4.  Also I am using "calCreateSpecialFunctionsForm"  but it seems like it would be more flexible to perform it's function myself to make a more advanced form. I could use "calRegisterSpecialFunction" to register the function, and "hiCreateForm" to open the form.  Is there anything else I need to take care of when I do this?  Would I then need to use the form functions without "a" appended?