Your first problem is caused by evaluation operator after the function definition. Get rid of it and your troubles go away.

I have no idea why your second problem occurs. It works fine in Mathcad Prime 10.0 and I see no reason to suppose that it does not work in Mathcad Prime 9. This is why experienced Mathcadders recommend that you post a worksheet with the problem in it. There are some subtleties, such as Math Styles or Greek vs Latin characters, that don't necessarily show up very well in a screenshot.
Ah, in fact, looking closely at your screenshot, did you use the subscript operator ctrl-minus or the index operator [ to insert the i? A subscript in a name is just a decoration and the i forms part of the name. An index i is a separate name.

I'd post a worksheet but it wouldn't be much use to you as Mathcad Prime files aren't backward compatible.
Stuart