Lectrician

My friend is using an iPhone 3 with the older Groundspeak software. She went to update to the newer one, and deleted the old one as recommended first. She is saying she now gets an error saying she needs iOS 4 or later. Is iOS 4 the operating system for the iPhone 4, or is this something that can be updated on the iPhone 3? Is there away to get the older app back now it's deleted? Appreciate any pointers!

Since updating I can no longer log in with the app! It asks for my login details, shows me a page to accept a connection to geocaching.com, and then a big error pops up from the website by the looks of it saying there was a connection error. I have tried many times, power cycling the phone too. How can I go back to the old version? I want to go caching!