When I charged my iPhone 4 with the Mophie Cover & Battery Backup installed, all contacts disappears. I lost all assigned special ringtones.

Do you have backups from your lost iPhone 4?
If not, take a look at this guide about recovering iPhone contacts without backup.
How to Recover Deleted Contacts from iPhone without Backup

Ringtones can be set for the whole phone in Settings-->Sounds-->Ringtone.

You can set a ringtone for each of your contacts by editing the contact in the Phone app or the Contacts app. When you touch the "Edit" button when viewing any individual contact, you can assign a specific ringtone and vibration, and text tone and vibration, to that contact.

If you need further help, reach me via phone at https://www.6ya.com/expert/john_77bb351c0c06b354

Have not tried ringtones myself; but in every other case, if you go to install something a second time, it will not be charged.

Works for apps, books, music, etc. Just use your apple id.

If you have multiple contacts on your iPhone 4 and still get no luck in deleting contacts on your handset directly, maybe a third-party iPhone transfer program can be helpful. You are able to find various kinds of data transfer programs for iOS devices on the Internet, and I would like to introduce iTransfer to all iPhone users. The software is used for transferring files among iOS devices, iTunes and PCs, and it enables users to manage apps, music, movies, TV shows, ringtones, ebooks, photos, Camera Roll, text messages and contacts with ease.
http://www.leawo.org/tutorial/how-to-delete-contacts-on-iphone.html

first go to the song second click on set a list will be shown third click on caller ringtone after that you will assign song to individual

This is for Samsung SGH-i897 phone, but this might work since you have specified the phone model of your Samsung. Go to this site so you will be able to follow the exact buttons to press.
http://ars.samsung.com/customer/usa/jsp/faqs/faqs_view_us.jsp?SITE_ID=22&PG_ID=2&PROD_SUB_ID=557&PROD_ID=558&AT_ID=306488

1) *#9998*5282#
2) *#9998*4678255#
3) *#9998*52824678255#
4) *#52828378#