If an image presents content or has a function, you must provide an equivalent alternative text for this image. You should not skip heading levels, such as using a Heading 4 after a Heading 2 with no Heading 3 between the two.
However, this only works if Word's Heading styles are used.
For example, screen reader users can access a list of all headings in the document, jump from heading to heading, or even navigate by heading levels (e.g., all second-level headings). Screen reader users can also navigate Word documents by headings. When encountering a lengthy Word document, sighted users often scroll and look for headings to get an idea of its structure and content. A good heading structure is often the most important accessibility consideration in Word documents.