Firmware transfer *bin from Android to uC

"The firmware is loaded in uC successfully."
"[...] but it seems that the user code is changed when using Android OS."

The above two statements are opposites. No transfer that damages the transmitted file can ever be classified as "successful".

So - what was the result of your comparison of the files? How did they differ? Where did they differ? Was there a change in file size? Was there some ASCII file conversion, converting end-of-line characters in the belief that it was a text-file transfer? Was random bytes damaged? And have you verified if the difference was within the used range of the binary, or if the changes was in bytes after the file was expected to have ended?

If you make the transfer twice in a row - is the resulting data in the microcontroller identical or different, i.e. is the garbling random or repeatable?

And note that an Android device have access to more than one application with file-transfer capabilities. Have you tested if it matters what application you have used?

You make it sound like this world just have "Android". The Android operating system exists in a huge number of different versions. And each hardware manufacturer packages their devices with different application programs. So "So, I’m curious if someone has successfully transferred the firmware from Android to uC, using USB bootloader." is normally a too general question to be applicable. If a specific HTC phone with a specific set of updates is able to upload a binary ok, it doesn't tell much about the results for a Samsung tablet with completely different Android version and installed apps and system tools.

"The firmware is loaded in uC successfully."
"[...] but it seems that the user code is changed when using Android OS."

The above two statements are opposites. No transfer that damages the transmitted file can ever be classified as "successful".

So - what was the result of your comparison of the files? How did they differ? Where did they differ? Was there a change in file size? Was there some ASCII file conversion, converting end-of-line characters in the belief that it was a text-file transfer? Was random bytes damaged? And have you verified if the difference was within the used range of the binary, or if the changes was in bytes after the file was expected to have ended?

If you make the transfer twice in a row - is the resulting data in the microcontroller identical or different, i.e. is the garbling random or repeatable?

And note that an Android device have access to more than one application with file-transfer capabilities. Have you tested if it matters what application you have used?

You make it sound like this world just have "Android". The Android operating system exists in a huge number of different versions. And each hardware manufacturer packages their devices with different application programs. So "So, I’m curious if someone has successfully transferred the firmware from Android to uC, using USB bootloader." is normally a too general question to be applicable. If a specific HTC phone with a specific set of updates is able to upload a binary ok, it doesn't tell much about the results for a Samsung tablet with completely different Android version and installed apps and system tools.