Upgrade to Big Sur Failed & get stuck at loop for install & Failed

Hello everyone,

Yesterday, I updated my Macbook Pro ( Mid 2015 ) to Big Sur, But it's fail & run to infinite loop install when I start & log in to my account

1. Error when upgrade to Big Sur:

2 - When I restart & login to my account --> It's automatic reinstall again ( can't login to desktop screen again & have to wait about 30 minutes for install & fail again )

3 - Try to boost with Recovery mode ( Command + R ):

• Can't unlock boosted encrypted disk with user / password ( it always say that: wrong password )
• Try unlock using iCloud account --> it says: "The supplied iCloud account was unable to unlock this volume"

My questions are:

1. Is there any way to access my disk to save data & free more hard disk space ( I guess error maybe occur because lacking of disk space) ?
2. In this case, can we use Target Disk Mode to access hard disk through thunder bolt port ?
3. Is there any way to pass through problem or I have to erase & install new OS ?
4. Bring it to Apple Service can fix this problem or save data ( or no way ) ?

Thank you!