"(original)": I do have the original from from 2021 when I was happy with it and have been using it every day since then.
"I don't understand": My app was finished and then along came android 13 which changed BLE. I wanted to change buttons from simple buttons having text to ones that would have images. Text doesn't fit on all screen sizes but images auto-resize. Along with this I wanted to do a few other nifty things. My first attempt in early 23 did not work. BLE said it updated but HeartRate.aix would not work. The app would no longer measure heart rate.
I live here on this island for only 3 months then I go to my home on another island for 3 months back and forth. On the other island I am offgrid so when I returned here to ongrid island this time, I once again gave BLE another shot. The new version of BLE did update and I merrily set upon a few frivilous improvements.
"I would have dozens of backup copies of that app": If you have been reading this post I did say I have MANY backups. I had over 20 of them. I am very happy with the smooth and efficient methods I have made and if the package name is screwed up it does not matter!!! So ... this post was not coming to a solution and as of post 38 I chose to eliminate the multiple backups and create only two. If I make more changes (which I doubt) I will progressively make more again.
Package name versus file name: You said "it is impossible". Create a simple app and then change the name of the aia file on your computer? you will find that the package name inside the aia is different from the file name! That aia name will produce an apk of the same name but the package name is different! It is obvious to me now (thanks to @ChrisWard post 34 & 59) that I did this. Also thanks to @Anke for providing me with a means to see where the package name lives so that I could understand my confusion.
I hope now, after lengthy explanation, that this all is understandable