While holding the buttons, connect the phone to the PC via USB cable.
Obtain the correct official firmware file (usually .ofp or .ops ) specific to your device model. msmdownloadtool v1.8.6
Some modified versions of 1.8.6 can work offline without requiring an authorized service center User ID or password for older security patches. How to Use MSMDownloadTool v1.8.6 While holding the buttons, connect the phone to