I upgraded an app on my iPhone 4, but this new version doesn't work. How do I replace for the older version? I did the stupidity of upgrading the newest version of AM 880 KIXI radio, a retro radio station in Seattle. The version I had was the previous one, the 2.8 and I held off upgrading for a long time, but in a moment of insanity, decided to do it and deleted the app and downloaded again on the AppStore, thus downloading the 3.6 version, the next one after the 2.8- i tried uploading directly, but I kept being redirectioned to the app itself, that's why I deleted before downloading again. 
The thing is my internet connection isn't that good, but the app always worked fine, but now with this version it keeps buffering at lot and it doesn't even show the music that's playing anymore, even when my connection is speedy. Is there any way to undo this? I have an iPhone 4 that hasn't been backed up to a computer, so I don't have the previous version saved as a .ipa file. I have iOS 7.0.4.  Seriously, what do I do? I know I sound desperate, but I listen to this station very single day, specially during work(I'm a translator) and it's essential for me to help concentrate. Is there any way I can retrieve the previous version of the app I was using? I also tried clicking on app support, next to the reviews on the AppStore to try and get in touch with the developer, but I keep getting 404 error. Seriously, I really need the 2.8 version back on my phone- I beg for help. 
If it's necessary, I will jailbrake my phone, but as long as it's guaranteed I can have the 2.8 version of that app and download it.
Do you have a backup? Time Machine or otherwise? If so you can restore the file from a backup.

The iPhone apps are located in ~/Music/iTunes/Mobile Applications and end with the ".ipa" extension.

It has been a while since I tried this but I think you just have to place the restored file in the proper folder and sync your phone.