Reset code i need master code for experia st23i

see if this helps you out.
Hard Reset SONY Xperia Go ST27i

1. Switch off your phone.
2. Then hold and press together Power button + Volume Up for about few seconds, or until you see menu of your screen.
3. Follow the instructions on your screen, and confirm operations.

How to Hard Reset my phone - SONY Xperia Go ST27i - HardReset.info

or this link.

https://www.google.com/search?q=how+to+reset+a+sony+experia+pm+0090bv+st27i&rlz=1C1AVFC_enGB797GB798&oq=how+to+reset+a+sony+experia+pm+0090bv+st27i&aqs=chrome..69i57.9658j0j8&sourceid=chrome&ie=UTF-8

https://www.safeunlockcode.com/sony-ericsson/unlock-xperia-miro-st23i


This site will give you the unlock code.

1. Make sure the battery charge properly before doing this step
2. Do not forget to backup all important data
3. Turn off the SONY XPERIA MIRO (ST23i/ST23a)
4. Press and Hold together: Power Button + Volume Up Button for several seconds
5. Follow the menu at LCD screen to continue the hard reset SONY XPERIA MIRO (ST23i/ST23a)

Hi James,
I have this link for you which is a forum for resetting Sony Experia phone since you do not provide here the model of yours. Hope it helps.
Xperia SP hard reset problem Support forum

Hi James,
I have this site for you which is a forum on how to reset Sony Experia phones ( hope one that is the model of yours ). Hope it helps.
Xperia SP hard reset problem Support forum

since you tried everything, the best solution would be doing a factory reset on yout Sony Xperia phone.. but you have to backup your files on a computer first. To reset it, follow the ff steps below:

1. Make sure the battery is not empty, better fully charge
2. Turn on SONY XPERIA MIRO (ST23i/ST23a) smartphone
3. Don't forget to backup all important data
4. Go to menu: Setting > Backup & reset > Factory Data Reset > Erase internal storage > Reset Phone
5. Choose Erase everything to continue and confirm you ready to do the format SONY XPERIA MIRO (ST23i/ST23a)
6. The SONY XPERIA MIRO (ST23i/ST23a) will continue the step until ready to use in clean factory default.

Option : Hard Reset SONY XPERIA MIRO (ST23i/ST23a) with Hardware Key Button:

1. Make sure the battery charge properly before doing this step
2. Do not forget to backup all important data
3. Turn off the SONY XPERIA MIRO (ST23i/ST23a)
4. Press and Hold together: Power Button + Volume Up Button for several seconds
5. Follow the menu at LCD screen to continue the hard reset SONY XPERIA MIRO (ST23i/ST23a)

Hi, what kind of lock has your phone been locked to? If it is a phone lock or a pattern lock, Take your phone to the nearby service center.
If it is a network lock, Visit www.TheUnlockSpot.com and get the unlock code for your Sony xperia ST23i at affordable cost with easy unlocking guide. Good luck mate.

You can unlock your Sony Ericsson Xperia X8 by using unlock code.To get this code at low cost visit the site Simpleunlocking.com here you need to specify the IMEI number of your phone,Country,Network provider to which it is locked.Then they deliver the unlock code to you through mail.Using that code you can unlock your phone easily.After unlocking from Network lock,you can use any GSM network Sim card on your mobile.