Rex is correct, but IMO the update (to be fully USPAP complaint) requires much more than just the form an the attached prior appraisal.
1. It is a different market; "different" may mean no change, but it should be reanalyzed. IMO, a 1004MC would be sufficiently adequate.
2. Whatever sales you consider should be summarized (technically, the approach you use... which would be the sales comparison approach... should be summarized along with the data so the reader can understand and evaluate your conclusions). If this is a simple assignment, a simple narration of the sales is sufficient (IMO). If this is a complex assignment, something more than a narration might be warranted.
3. You need to include a new certification; don't forget to make your prior service statement.
The above is necessary for any "update" using the 1004D form if one wants to meet the USPAP minimums.
Your situation adds an extra "twist"; you originally valued the subject based on the HC that it was complete per plans/specs as of the date in the past. You've gone out and verified that the work isn't done, so it still isn't complete.
You can appraiser the subject using the update process, but you'll need to confirm with the client if they want it "as is" or "subject to completion".
If they want it "as is", I'd charge the same amount of money as I would for a brand new appraisal since I'm now going to have to analyze the market impact of the unfinished work.
Remember: the 1004D form is simply a convenience for the client; it alerts residential lenders and the GSEs that the appraisal (an update is an "appraisal") is based on a prior appraisal and the original report has significant appraisal reporting requirements (without the original report, the new appraisal cannot be properly understood).
An appraisal is an appraisal. The 1004D by itself, and even with the older report directly incorporated, does not meet the minimum requirements of SR2. The appraiser must make sure that the new appraisal meets those requirements. This means supplementing the old report and that one-page form with the necessary analysis and certification so that all together, it meets the requirements and provides credible results.
Good luck
(my "updates" are typically 6+ pages, and that doesn't include the old report or the new signed certification; and yes, I charge more than the $100 to $150 many clients expect to pay).