Howard Miller

$CFG->theme='boost';

Looks to me that you've somehow mixed up old and new versions of code.

Either that or you're trying to use a theme that is incompatible with this version of Moodle (i.e. too old).

I think you're going to need a custom theme of some sort. I'll move this to the Themes forum.

What aspects do you want to customise?

You don't say what version of Moodle you are using, but I think we can reasonably presume that Dataform is an abandoned developement. The latest release was for Moodle 3.3 over six years ago.

It's probably the time to find an alternative solution.