How to Downgrade your Twitter (for iPhone), or any iOS app. *
This article covers how to downgrade for both non-jailbroken and Jailbroken iPhones. If you do not have the file needed to downgrade normally, you must resort to the Installous tweak.
Downgrading a Version of an App normally (No Jailbreak):
1.) Search your Recycle Bin/Trash for (ex) Twitter 3.5.1 .ipa. It may be a hidden file, so enable Hidden Files and Folders by typing in Terminal “defaults.write.com.apple.finder AppleShowAllFiles TRUE. (Windows users can edit Folder Settings in Control Panel) Drag it out of your trash can and onto your Desktop.
2.) In the App pane in iTunes, delete the specified App simply by right clicking it and selecting Delete. YES, move everything to the trash. You don’t need to go back to the Trash as you are going to replace 4.x.x with Twitter 3.5.
3.) Drag Twitter 3.5.1 .ipa into iTunes. It doesn’t matter where, since iTunes will stick it in the app drawer automatically.
3.1) If you want to double check, Select the Twitter app you just synced in iTunes and Get Info. Under the Account Name, it should read your Apple ID. If it does not, you CAN use another Apple ID, but it must be registered with your computer. To do so, go to Store<Authorize Account and enter the specified ID and password. No crack required since the app will be signed to that ID.
4.) Sync. Your Twitter information may be gone, but re-logging in should restore everything
Downgrading via Crack (Jailbroken devices only)
1.) Make sure your device is Jailbroken. If your iDevice is not jailbroken, you find out how to do so here.***
2.) Open Cydia and Navigate to the following: Manage<Sources<Edit<Add. Now add the following Repo (URL): http://cydia.hackulo.us/
3.) It should Add, and/or prompt for a Respring/Reboot. Allow that, as always.
4.) Once the source is added, search the Repo for Installous 4. (Note: I have not yet tried AppSync for iOS 5.0 and above, so I’m writing this for use with Installous). Download the Installous package and Respring/Reboot.
5.) Now, you will repeat the above guide (normal downgrade) but instead, use THIS FILE. It is a cracked version of Twitter 3.5. With Installous, you’ll be able to sync it without problem. Huge thanks to @most_uniQue for the crack.**