Howard Miller

This seems a little confused.

Your subject says "require course for just some students". Well, that's what courses do - you only enrol the students you want to have access. Then in your text you say, "but leave completion optional for some while making it required for others". Which I don't really understand. Can you explain in a bit more detail what you are trying to do?

Generally, any kind of restriction is likely to involve Groups and possibly the Restrict_access feature.

You could use Restrict_access to control access to a Page_resource. However, I wonder if you have something rather more "fancy" in mind.

The file is somewhere on your server's file system - so you (or someone) will need access to that.

If you want to find the location, (in Moodle) go to Site admin > Server > PHP info. Near the top it tells you the php.ini file(s) that it is loading. These days, the settings are often spread over multiple files. At least you can tell your IT admin.

....careful... my similar response seems to have been deleted. Which is a new thing...

No.

Moodle requires a fixed wwwroot to be configured. Note "fixed".