i forgot the password to my ipod touch4

You do not find but have to restore the iPod

iOS: Wrong passcode results in red disabled screen

Connect the iOS device to your computer and restore via iTunes. Place the iOS device in Recovery Mode if necessary to allow the restore.

If recovery mode does not work try DFU mode.

How to put iPod touch / iPhone into DFU mode « Karthik's scribblings

For how to restore:

iTunes: Restoring iOS software

To restore from backup see:

iOS: How to back up

If you restore from iCloud backup the apps will be automatically downloaded. If you restore from iTunes backup the apps and music have to be in the iTunes library since synced media like apps and music are not included in the backup of the iOS device that iTunes makes.

You can redownload iTunes purchases by:

Downloading past purchases from the App Store, iBookstore, and iTunes Store

If you encrypt an iPad backup in iTunes and then forget your password, you will not be able to restore from backup and your data will be unrecoverable. If you forget the password, you can continue to back up and use the device, however you will not be able to restore the encrypted backup to any device without the password. You do not need to enter the password for your backup each time you back up or sync.

If you cannot remember the password and want to start again, you can use a SmartKey iTunes Backup Password Recovery to unlock iTunes backup password at first.