Term to describe how much something has changed from its original configuration

Solution 1:

It's doubtful that you'll do better than complexity for a situation as general as you describe. You are talking about steps, but what's a 'step'? The closest thing that comes to mind is a string metric, a measure of how different one string of symbols is from another, of which there are several (see e.g. here). One of these, for example, is the Levenshtein distance, which, roughly speaking, is

the minimum number of single-character edits (insertions, deletions or substitutions) required to change one word into the other.

In physics, particularly quantum mechanics, there are various ways to quantify the 'distance' between quantum states (see e.g. here). This seems quite close to what you are asking—except that, as far as I know, they do not involve the notion of 'steps'.

In probability and statistics, there is a notion of statistical distance. But again, the various kinds of statistical distance don't involve the notion of 'steps'.