Install CM12 based on Android 5.0 Lollipop for Galaxy Ace 3 GT-S7275
Android community has a habit of adding new features and interface unofficially. This is why third party developers do work on custom firmware. Recently, an unofficial CyanogenMod 12 build based on Android 5.0 Lollipop appeared for the Samsung Galaxy Ace 3. This is a chance to experience the latest trends of Android. Since this is a custom ROM, you can experience many bugs with it. But it is quite functional and many features are working fine. You can experience errors with NFC, Stock Camcorder crashes (use google camera for now), and Home button does not wake up the device. There are may be some other bugs, but it is worthy to give this CM12 ROM a try, at least when you are not willing to wait for an official Lollipop update. Will Galaxy Ace 3 GT-S7275 receive the Lollipop update? It is still not confirmed, as far we know.
CyanogenMod has been a popular way to enjoy the stock and latest Android versions. But it can bring you huge customizations. To load it on your phone, be sure to have a better custom recovery like TWRP and ClockworkMod. Download and place the ROM zip file and Gapps package to your phone. Boot phone in recovery and start installation. But take nandroid back and perform wipe before you get started. For downloads and instructions about this Galaxy Ace 3 Lollipop ROM, you can check this XDA thread.