Using a Function within an Assignment

Hello there! First time poster. I am playing around with creating functions in ROBOTC and have a couple of questions I was hoping the community could help answer. I didn't want to overload this one post though since each question is a little different, so I'm going to break it up into a few posts

I have read on these forums

Ford Perfect's code for rounding a float into an integer (very helpful, thank you so much!). I am wondering if ROBOTC will allow me to use this function (or any function for that matter) in an assignment if that assignment falls within a declaration.

Also, can I use mathematical expressions in an assignment if that assignment falls within a declaration?

And lastly, a bit off topic, but can I call a function within a declaration/assignment (or really anytime at all) by inputting a mathematical expression instead of a variable?

Will that pipe through or do I have to do the calculation before calling the function (using some sort of a temporary variable) because functions can only handle variables as inputs?

Thank you for the help!