Yes, you can upgrade your device to the compatible latest version via Samsung Odin. Technically, [https://en.wikipedia.org/wiki/Samsung_Galaxy_Alpha|Samsung Galaxy Alpha] can be upgradable to 5.0.2 (Lollipop). Although you cannot receive the Software updates, you can completely wipe the current firmware and flash 5.0.2 (Lollipop) firmware on your device using the Samsung Odin, which is the official stock firmware flashing tool for Samsung Galaxy smartphone.
* First, download the Odin flashable firmware file for your device. (This [https://www.xda-developers.com/download-stock-odin-firmware-samfirm/|XDA thread] will help you)
* Now, extract the firmware file and there you will be able to find out five MD5 files
* Install USB drivers on your computer if you have not installed yet
* Then, [https://odindownload.com/root-android|download Odin] program on your PC (No official site and use download resource you trust and Odin3_v3.09 Recommended for Kikat )
* Extract the file and run the Odin program as "Admnistator"
* Turn off your device
* Press & Hold Power+Volume down + Home buttons at the same time until you get the "Download/Odin Mode"
* Next, connect your device to the computer using a USB cable
* Launch the Odin program and check the "Log Box" area and you will see "Added" and also the ID: COM area will become Light blue that you can find on the top the program interface
* Next, click the soft buttons (BL, AP, CP, CSC) on the Odin interface and load the each extracted file (Check first two letters of the file name to identify the correct file for the correct key)
* Always load the "HOME_CSC file" for "CSC" button to avoid wiping phone’s data and settings
* After loading all the files, click on the "Start" button
The whole process may take up to 10–12 minutes and the device will reboot finally. Most probably device takes a bit longer time than a usual reboot time.