Versions around v25.x.x are typically the final stable builds for Android 4.1.2.
Sideloading any APK carries risk. Android 4.1.2 has not received a security patch in nearly a decade. Here is how to stay safe: play store apk download for android 4.1.2
By default, Android blocks installations from sources other than the Play Store (which you don't have yet). You must bypass this security setting. Versions around v25