After scouring XDA Developers Forum and 4pda (Russian legacy forums), these are the most stable builds available today.

Android Legacy Hub Reading Time: 8 Minutes

By today’s standards, the stock operating system (Android 4.1.2 Jelly Bean) is not only outdated but virtually unusable. Apps crash, the UI lags, and security vulnerabilities are rampant.

Since this device is quite old, many original download links on forums like XDA may be dead. You might need to dig through archive sites or specialized Telegram groups for the S5310 community.