How would you produce the alternative image.
Me, personally, would plug my phone into my computer and try to use it as a flash drive with recovery software running from the computer (you wouldn't run anything from the phone). I'm not sure how the image creation would work though, and I know my way would be bad say if there was a debug file that got written to in the process of connectiong and disconnecting or the recovery software was too strong for to not affect the memory card too much.
The problem with using it as a flash drive is the phone would still be writing data in the background as there's services still running to keep the phone operating. I would recommend getting the copy and then turning the phone off rather than keeping it on and potentially risk writing data over the existing data.
There's a few programs out there, but I can't vouch for their security and effectiveness. For example, one is called Magnet Acquire and another one called Oxygen Forensics. But, again I can't vouch for it's ability to do the job. OP can search up forensic tools which are compatible with android or what ever software the phone is running and take it from there.
You can just dump the backup image (honestly not an image it's firmware) you can dump the firmware with simple tools, but most of the smartphones have different CPU model, look at the Samsung you can't easily dump the firmware without using Z3X box, it is a tool, which is used by technicians including me.
There are phones that you can easily dump your firmware mostly MTK CPU, there are many tools that you can use like sp tools, but you need to enable your debugging mode.
@OP if you are looking to recover your bitcoin wallet from a formatted phone you couldn't recover them back using those tools.
Base on what I experienced with wondershare you can only recover images, videos, apps and songs, but the files or data of apps are totally erased you will never get them back unless if you have a backup from android recovery mode (You can open recovery mode by holding 3 keys from your phone) or if you fully backup your firmware.
If you still wanted to try to recover your formatted or erased files from your phone you can follow this guide
https://www.wondershare.com/data-recovery/wizard-mode.htmlHowever, it's not guaranteed that you can recover the files you wanted, most of them are broken.
Thank you for your information. Do you know any trusted people in this forum who have already had such a case and have managed to deal with it?
Do you know of any good sources with more information? What blogs, if any or somethink like that?
What model of your phone? if it is android phone XDA-developer forum is a good place.
