Samsung galaxy s3 touchwiz home has stopped working

go into the touchwiz app and clear the cache. it might help to restart your phone every now and then.

Scan for viruses / factory reset/ use alternative launcher

Your Samsung Galaxy S3 must be restricted to some specific network. That is why it allows only emergency calls when a SIM card from some other network is inserted in. You need to unlock your Samsung Galaxy S3 to make it work with all SIM cards. You can unlock your Samsung Galaxy S3 safer and easier using unlock code. You can get the accurate unlock code for a Samsung Galaxy S3 from Unlock-Zone.com at affordable cost. Good luck.

-<()>--<()>--<()>--<()>--<()>--<()>--<()>-
..............UNLOCKING INSTRUCTIONS..............
-<()>--<()>--<()>--<()>--<()>--<()>--<()>-

Method 1:
1 - Switch ON your Samsung Galaxy S3 with a NOT ACCEPTED SIM Card.
2 - Samsung Galaxy S3 will ask for "Password".
3 - Enter the Unlock Code.

OR (if the Samsung Galaxy S3 shows "Insert Correct SIM Card")

Method 2:
1 - Switch ON your Samsung Galaxy S3 with a NOT ACCEPTED SIM Card.
2 - Don't bother about what's being displayed on your Samsung Galaxy S3.
3 - Compose : #0111*CODE#.

SOURCE: MobileUnlockGuide.com

Full reset. Instruction manual or there might be small pinhole to reset, not sure.

Get the unlocking service from an online vendor like
http://www.wickedunlock.com/samsung-galaxy-s3/rs11wp9/ to unlock your Samsung Galaxy S3 from network lock.To get the service you need to submit your country name,currently locked network provider name and IMEI number.

Well, first of all, your mom doesn't want you running up the wireless data bill. 2nd of all, buried in the SETTINGS menu is a selection to turn DATA on/off. Go find it and turn cell data back on.

You can Contact your network provider and request an unlock code
Insert your new SIM card
Power your Samsung phone on then enter Unlock code.
For more details you can check at Samsung India site.
Samsung Galaxy S3 Price India Buy 3 Smartphone Features Reviews Specs

it will be a screen problem so contact samsung service center