Not able to copy RAW files in any of the ways to my Windows PC or other devices.

I am having iPhone 12 Pro Max and most of the times while I take photos I shoot in RAW (DNG) format. I have disabled the Photos to iCloud. But to edit the RAW file(s) I am not able to copy in any of the following methods to my Windows 10 PC or my Android Tablet (Samsung). The methods that I tried are as follows:

1. Connected the iPhone to the computer through a USB device. Opened the Internal Storage/DCIM/100APPLE. I see the DNG files. But when Copy and paste is given it says: "The device is unreachable". I even tried the SETTING. Under that PHOTOS and the "Keep Originals" is ticked or selected.
2. Connected the iPhone to the computer through a USB device. Under Start Menu of Windows 10, go to Photos and Import from a USB device. There my RAW images are shown. But when I select the photo(s) and try to import, it says "Something went Wrong" "Your files might not have been imported".
3. Select the RAW (in DNG) format and SAVE it Files folder (in iPhone) under a created folder. But the RAW file always stores in JPEG format. It doesn't gets copied in RAW format.
4. Even if I try to open the RAW file in Snapseed that is installed in my iPhone, it still opens in JPEG format.

The photos that I have clicked in RAW format has a RAW watermark in left top of the image. So I assume that the files are indeed in RAW format.