Attention :
After hard reset you lose everything on phone
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How to Hard reset :
1.When you see mobile shows google lock Or pattern click on emergency call


3.After type you see
*service info
*service setting
*service texts
*customization setting

4.select customization setting

5.Select reset customization

6.In the last Click on Reset Customization and reboot

After reboot hard reset is complete !!!!!
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I test this way on:
St15 - St18 - Sk17 - Lt15 - Lt18 - Mt25 - St17 - St21 - St25 - lt26 - Mt11 - St26 - And................
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If this way not work :
If this way not work on your phone you shoud flash it .(flash with setool Or Flashtool Or Update service Or EMMA