This guide will work for any Samsung smartphone (other phones have different backup methods, Recovery menu combinations):
Please Factory Reset your device in the following manner if you are facing any annoying issues after you update your phone to a new MAJOR Android / One UI version so you will get a 'fresh' experience:
**IMPORTANT POINTS (READ BEFORE RESET) -
After taking necessary backup from Internal Storage, like Contacts, Messages, Apps, Home Screen layout, Wi-Fi, Bluetooth settings, etc. (Samsung Smart Switch app is best for this).
** You may need to login into all the apps (great if you have saved login info on Samsung Pass or Google Smart Lock), or lot out and log in again BEFORE Factory Reset to 'remember' your passwords
** You can also backup WhatsApp chats from WhatsApp settings (chats -> backup) just before reset. WhatsApp-specific default media (images, videos, audio, documents, etc.) is located in Internal Storage -> Android -> media -> com.whatsapp-> WhatsApp -> Media.
** You can also backup Games data (if it's offline, no issues for online as it will sync from cloud).
I think Samsung Smart Switch only backs up 'apps', not app data.
Just keep a copy all the folders of your favorite installed games from Android folder (obb, data) and paste it back again in same folder layout after reset.
Also make sure you have Samsung backup codes just in case (you can generate them from Settings -> at the top Samsung profile security settings. Sometimes OTP message does not arrive for Samsung login (if you have forgotten Samsung password) so...
1. Once you are on Android 12 One UI 4.0, keep your phone connected with cable (otherwise Recovery menu won't be triggered) and Power Off phone.
2. Hold Vol. Up and Power button, release Power button when you see boot screen (but keep holding Vol. Up button).
3. On Recovery Menu, first Wipe Cache.
4. Then Wipe Data / Factory Reset.
5. Then again, Wipe Cache.
6. Reboot and you can remove the cable.
Setup initial stuff and let the phone settle down for some time (a lot of app updates will trigger, phone may heat, which is totally fine after Factory Reset. It as good as buying new device.
Connect with cable again and using Samsung Smart Switch, restore all data.
The trouble is worth it as this method fixes 99% issues after any MAJOR Android update.
Keep the battery within 15-85% definitely do not let it drain down to 10%, 5% or 0 as nowadays Li-ion batteries do not require such harsh treatment.
Do not judge the battery life in 1st week, let it 'learn' from your usage patterns and put unwanted apps, games to Deep Sleep from Battery settings.
Yes, this process will take some of your precious time but it is totally worth it. Do it over a weekend.
Finally, enjoy a fresh & smooth experience of One UI 4.0 Android 12.
There will be no issues at all if you exactly follow the steps as mentioned above but since it is a tradition and rarely things may go wrong IF you peform wrong steps, here is a disclaimer:
DO IT AT YOUR OWN RISK.
