Oppo released the September 2021 security patch for Oppo A31. It is a mid-range budget. Surprisingly Oppo has not yet released any major software update for Oppo A31 except for security updates. Android 10 should be the first OS update for Oppo A31(2020) But unfortunately, we don't think it might get any OS update now.
Oppo A31(2020) smartphone was released in 2020, February 14 with Android 9

According, to Oppo it won't be providing any OS updates for the device, it will just pop some random software/security update.
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ColorOS 12 Features & Rollout Plan | list of devices eligible

Source: Twitter User -->> Shubham Sharma
There is some amount of heating and high battery drainage issues, possibly as it's an almost 2-year-old device, Both hardware & software has pushed it high battery drainage issue
| Android OS | Update | Release Date/Status | Estimated months |
| Android 9(pie) | Out-of-the-box | February 2021 | nil |
| Android 10 | First OS update | No update | - |
| Android 11 | Second OS Update | No update | - |
The roadmap of android is not at valid, as it won't be getting any OS updates
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