From my other post on this:
I discovered how to stop the installation of the new android system upgrade (to 5.0 Lillipop from KitKat) if you have downloaded it to the Samsung S4 (but not installed it yet). The best thing is to keep saying "no thanks" to the upgrade "offer" that appears on the phone from time to time. If you accidentally said "OK to the download" but changed your mind, as I did after reading reviews of Lollipop, there's a way out.
Here's what I did. As the first post said, I wanted to stop installation of a downloaded system upgrade to Lollipop. I had downloaded it thinking that I would not have to install it, in order to stop the frequent "invitations". But once downloaded, you HAVE to install it at a certain time that day. The phone required me to say when I wanted to install, so I said 1 AM.
I then immediately cleared the system cache (this is harmless to your data and personal settings) by doing this:
Turn off phone
Remove the battery and reinsert.
Hold down the Home and Volume Up keys
Press and hold the Power button while still holding the other keys.
You will see small blue writing in the upper left corner. When you see it, release all keys/buttons.
Wait for the system restore menu in yellow to appear and a little robot lying on it's back
Press on the Volume Down to scroll down to "Wipe Cache Partition."
Press the Power button to select it.
Wait for a few seconds for the phone to clear the data.
Then press the Power button to select "reboot system now." (should be preselected)
Wait for your phone to reboot.
That night (before midnight as I had told it to upgrade at 1 AM), I turned off the phone and removed the battery (This step might not be required, but it's what I did)
For my wife's phone, we had checked the box "install automatically" when we "allowed" the download of the update, and on mine, I didn't check that box.
For my wife's phone (having checked the "install automatically" box), when we turned the phone back on the next morning it came on, then turned off (trying to do the system upgrade) and then the little android robot appeared with "Error". Later on, on the home screen, a message appeared "system update unsuccessful, no changes were made." Then everything was fine.
For my phone, where I did NOT tell it to install automatically, a message box appeared saying the install was ready, option is to install now or later. I pressed "install now" and the phone turned off, then behaved as above for my wifes phone.
The update DID NOT INSTALL and the phone was just fine in every respect, BUT WITHOUT LOLLIPOP being installed against my will. I like the KitKat build, my phone is working fine, and my motto is "if it ain't broke, don't fix it"
As mentioned, I had called Verizon asking what file(s) to delete to avoid the update from happening. The Verizon tech rep was nice and called Samsung only to be told there was no way to stop the upgrade once you downloaded it to the phone. Could I know more than Samsung?? But this worked for me. Perhaps they don't want us to avoid the update...
It "appears" the Lollipop download is stored in cache. So it may have been possible that I removed the update by simply clearing the cache, and if so, then you might not need to turn off the phone (or remove the battery), but someone else can experiment with not doing that step!
I assume Verizon or Samsung will try to get me to agree to upgrade again, but next time I will say "NO THANKS!"
--The other option, which I have not tried, if you did the update but hate it, would require you to have a prior backup of your phone made before the update occured. Using the KIES3 software from Samsung or other backup software (or if your backup is in the cloud), theoretically, you could do a factory reset of the phone, and then restore your phone to the last backup state BEFORE the Lollipop was installed. But this would only work if you had been making complete backups on a regular basis. This just reiterates the importance of making regular complete backups as phones are now as important as our computers.