I have a Sony Xperia Sola, but can not install IMO. Which version is better for that?
IMO requires a phone with Android 4.0 and up. As I can see from specifications, the phone is available for upgrade to Android 4.0. Download PC Companion, then connect the phone and click on the Support area in PC Companion. Follow the procedure to update the phone and then try installing the IMO application. It's not recommended to install IMO from a 3rd party website to avoid malware.
Download PC Companion: http://support.sonymobile.com/global-en/tools/pc-companion/