First, an automatic table of contents is far better than manual one. This requires that you use styles consistently for your headings that you want in the TOC.
How to create a table of contents in Microsoft Word by Shauna Kelly
As Graham pointed out, you can have the TOC point to styles other than heading styles. This automatically has hyperlinks.

Second, yes, you can hyperlink to any place you want in a document. You set a bookmark where you want the hyperlink. Assume you want something in your TOC that is in body text so you can't be looking for the style. Select what you want to appear in the TOC and bookmark that, assigning a name. Then, in your manual TOC you use a Ref field to both reproduce what you had bookmarked and have it be a hyperlink.

IMO, you would be better off going back through your document and consistently using heading styles and then using the built-in TOC feature. In the long run, it will save you time and hair-pulling. You do not need to use the formatting that comes with the built-in heading styles. You can modify the style to look however you want.

Generating a Table of Contents - Complex Documents
Understanding Styles in Microsoft Word
Basic Concepts of Microsoft Word - from Shauna Kelly