abbreviations - When to spell out or when the acronym itself is sufficient

When using an acronym for the first time, it must be spelled out. That's a given. However, if there is a "Definition" section where ALL acronyms that are going to be used in the document are defined and spelled out and this section precedes the rest of the document, do you need to use the full name and its associated acronym later in the document? Example: 1st paragraph of the document explains the document's purpose. In this paragraph, there is an acronym used as follows - "....Delegation Oversight (DO)..." "DO" is now identified as representing Delegation Oversight in the rest of the document. The next section of the document (which follows this first paragraph) provides definitions for all important words used in the document and provides their acronym (where applicable). Following this section is the rest of the document. Do we need to spell out each acronym or can we just use the acronym itself given that it is already defined? My thought is, if the acronym is already defined by the "Definition" section, it does not need to be redefined and spelled out at any point later in the document. Now, if this definition section was to be say on the last page of the document (like an index), then I would think that all acronyms would need to be spelled out the first time they are used in the document. Are these assumptions correct?