Please see the following:

• How to create numbered headings or outline numbering in Ribbon Versions of Word by Shauna Kelly and
• How to number headings and figures in Appendixes in Microsoft Word by Shauna Kelly
• Insert Cross-References

You can add cross-references to numbered items that have been numbered using these schemes. They semi-automatically change to update. However,

1. Cross-references are REF fields, they do not update instantly nor automatically. See Dealing with Fields in Microsoft Word
2. When you add a cross-reference to a numbered item it actually links to a hidden bookmark created by Word. If you need to add something before an item you have cross-referenced, go to the preceding paragraph and press Enter. Do not go to the start of an already-referenced spot and press Enter to have room. This will confuse the referencing and give very strange results.