meaning - English Subject-auxiliary inversion

In normal declarative English sentences, let's call them 'canonical' sentences, the verb comes after the subject.

• Bob is walking the Great Wall of China.



• Bob likes elephants.

But in other types of construction and in certain other situations the auxiliary verb comes before the subject. One notable instance is in questions:

• Is Bob walking the Great Wall of China?

Here we se the auxiliary verb BE occurring before the Subject. If there is no auxiliary verb in the normal declarative version of the sentence then we need to insert the auxiliary DO:

• Does Bob like elephants?

My question here is twofold. Firstly:

1. What are the different constructions or environments in which either we require subject-auxiliary inversion in modern English, or can optionally use it?*

Secondly, and more importantly:

2. Is there any generalisaton we can make about these constructions. Does subject-auxiliary inversion have some kind of meaning in all of these, or a subset of these?

*_{Not including poetry, for obvious reasons.}