You can still enjoy the Samsung Galaxy Ace 3 Marshmallow, though the device will no longer receive official updates. This means it is extremely beneficial to experience the latest OS on an outdated device. You can install a custom ROM firmware on your device so you can be up to date without having to buy new device. This can be done by installing the latest Android version on your old device. Make sure you follow this tutorial how to install the CM 13 custom ROM update into your Samsung Galaxy Ace 3.
Ace 3 Marshmallow Preparation
Since this is not official update, it is possible your device may get stuck during the installation process so it is recommended you install Nandroid tool to back up your stock ROM of the Samsung Galaxy Ace 3. This allow you to save your current firmware on your device so that you can then use it to revert back to the early state if the Ace 3 Marshmallow custom ROM will not run as expected. You will be able to make a custom recovery image necessary on the flashing process using the Nandroid backup. You also need to enable the USB debugging mode on your Ace 3. This can be done by navigating to Settings>About Phone. Tap on Built Number 10 times and then the Developer Options will appear. In the Developer options, switch on the USB debugging mode.
Ace 3 Marshmallow Update Installation Tutorial
Download the CM13 Ace 3 Marshmallow ROM file and the Google Apps package into your computer. Use the USB cable to connect your device into your PC. Copy the downloaded files into the SD card of the device and then disconnect the USB cable. Shut down your device and then start recovery mode. Choose Wipe Cache Partition, Wipe Data Factory Reset, And Wipe Dalvik Cache option in the recovery mode to clear all data. Now go back to main menu of recovery mode and choose Install Zip From SD Card option and then Choose Zip From SD Card. Search for the Android Marshmallow ROM file you have copied and then confirm installation of your Samsung Galaxy Ace 3 by pressing the Start button. Repeat the above steps to install the Google Apps package file. Once you have done all the installation, choose Reboot System Now option from the recovery mode menu. It will take a few minute longer than normal boot. Now you can enjoy the Ace 3 Marshmallow on your old device.