I was skeptical about updating the smooth running LE 8.2.2.3 version on my S912 box straight away as per ozarks advice, as I have already populated the box with all my media in 4 different profiles. The configuration of LE 8.2.2.3, adding my favorite skin and loading the media took me considerable time and I don't want to loose all this work.
So, I took a spare 16GB SD card and used it to install LE 8.2.5.1 using the LibreELEC USB SD Creator program. But this program has options to load *.img,gz, *.img,zip and *.img files. There is no options to load *.tar file. I took the option for showing all files (*.*) and selected the downloaded LibreELEC-S912.arm-8.2.5.1-444-1000nits.tar file. Then I wrote the image of this file on the SD card. After the writing was successfully completed, I tried to view the SD card's partitions but could see only a single Linux partition. There was no FAT32 partition (LIBREELEC). I sensed something was wrong and realized that this is not the way to install 8.2.5.1.
I again formatted the 16GB SD card and installed the LE 8.2.2.3. Loaded the new SD Card on the box and started LE Kodi 17.6. Copied samba.conf and remote.conf files to storage/.config folder. Rebooted the box and on my laptop opened the storage smb share and copied the LibreELEC-S912.arm-8.2.5.1-444-1000nits.tar file in .update folder and rebooted the box. On the restart at LibeELEC screen the system found the update file and completed the update process and rebooted. I checked the version and now it is 8.2.5.1. I tried various menu options on Kodi and found the response to be smooth and fast.
I loaded a H.264 and a HEVC H.265 video file on a flash drive, and tried playing them on the new updated box. The videos was playing smoothly and now there are no dark shadows in the videos. I was happy with the performance and it is better than my old LE 8.2.2.3.
I have made up my mind to update to the new LE version and removed the 16GB SD card, inserted the original 32GB SD card with LE 8.2.2.3 and my library, again copied the LE 8.2.5.1 update tar file and updated the system. Everything went well and I could see a better performance in this new version.
I also saw the "Boot to Android" command in Shutdown commands, which I don't remember seeing on LE 8.2.2.3. I installed android's "Reboot to LibreELEC" app on the box's android OS and now I have a dual boot Android/LibreELEC system.
One query here: I saw LE 8.2.5.1 as an update and not an image file ready to install fresh like 8.2.4.1. Is it still in beta or a completed project? I find LE 8.2.5.1 much better than LE 8.2.4.1. It is a good successful update.
Thanks to all who helped me.