Samsung Galaxy Pocket Neo (GT-S5310) is a legacy device released in 2013 with Android 4.1.2. While official support has ended, custom ROMs can refresh its performance by removing bloatware and potentially upgrading the Android version. Available Custom ROMs
Do look for Android 5.0+ (Lollipop) or newer. They exist as experimental builds but are unusable (1-2 minutes to open Settings). Stick to: galaxy pocket neo custom rom