Hello there,
After being banned my self, because of my friend who used my iphone to post pictures on my device.
I have been banned my iphone device permanently. So, after working 10 hours how to figure it, killing me, feeling bad.. i have finally figured out how to unban your device, and username. You will be able to UNBAN your username only, if its not removed by instagram.
In order to unban, You need a jailbroken device!
Follow my steps and you will be very soon back online:
1) Download "I-FunBox" install it on your computer.
2) Close all running apps on your iphone.
3) Open op Cydia and download UDID faker
4) Open up UDID faker and select "Instagram & Appstore" and change the device codes.
5) After you did that, close these apps dont RUN instagram leave it be.
6) plug-in your iphone and open up "I-FunBox" and go to: User Applications select instagram.
7) Open "Library", preferences empty the directory remove all.
8) Open "cookies" remove everything in it. And do it the same to "TMP" directory.
9) From the main "instagram" directory remove "iTunesArtwork" and "iTunesMetada".
10) close i-FunBox.
11) Restart iphone 4s.
12) Go to App store, create "NEW FREE" apple ID ask me if you dont know how.
13) Login to Apple Store
14) open up Instagram with your nickname and password.. and now it should work.
Peace
... please say Thank you for the help 
After being banned my self, because of my friend who used my iphone to post pictures on my device.
I have been banned my iphone device permanently. So, after working 10 hours how to figure it, killing me, feeling bad.. i have finally figured out how to unban your device, and username. You will be able to UNBAN your username only, if its not removed by instagram.
In order to unban, You need a jailbroken device!
Follow my steps and you will be very soon back online:
1) Download "I-FunBox" install it on your computer.
2) Close all running apps on your iphone.
3) Open op Cydia and download UDID faker
4) Open up UDID faker and select "Instagram & Appstore" and change the device codes.
5) After you did that, close these apps dont RUN instagram leave it be.
6) plug-in your iphone and open up "I-FunBox" and go to: User Applications select instagram.
7) Open "Library", preferences empty the directory remove all.
8) Open "cookies" remove everything in it. And do it the same to "TMP" directory.
9) From the main "instagram" directory remove "iTunesArtwork" and "iTunesMetada".
10) close i-FunBox.
11) Restart iphone 4s.
12) Go to App store, create "NEW FREE" apple ID ask me if you dont know how.
13) Login to Apple Store
14) open up Instagram with your nickname and password.. and now it should work.
Peace
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