On an iPhone 4 it IS possible if you have your SHSH blobs saved. You'll need to do some reading. If you've never jailbroken, you probably don't have them saved.
Only if you have previously saved shsh blobs for ios 6.1.2 for that particular device.
If you don't know what that is or how and when then there's nothing you can do.
Apple does not allow downgrades, if you ever need to restore you can only go up to the latest firmware version.
You can , search for the iOS 6.1.3 Ipsw file on the internet and the restore your phone ( when u hot restore press shift on windows or ctrl on a Mac and select ur Ipsw file)...YOU WILL NOT BE ABLE TO RESTORE YOUR BACKUP
You can , search for the iOS 6.1.3 Ipsw file on the internet and the restore your phone ( when u hot restore press shift on windows or ctrl on a Mac and select ur Ipsw file)...YOU WILL NOT BE ABLE TO RESTORE YOUR BACKUP
You can , search for the iOS 6.1.3 Ipsw file on the internet and the restore your phone ( when u hot restore press shift on windows or ctrl on a Mac and select ur Ipsw file)...YOU WILL NOT BE ABLE TO RESTORE YOUR BACKUP
You can , search for the iOS 6.1.3 Ipsw file on the internet and the restore your phone ( when u hot restore press shift on windows or ctrl on a Mac and select ur Ipsw file)...YOU WILL NOT BE ABLE TO RESTORE YOUR BACKUP