Two different situations, and only one of them is worth worrying about.
Strange behaviour after an outage (frozen menus, no network, odd input routing) is usually scrambled state, not lost data. Switch off, unplug for a few minutes, plug back in and restart. If it persists, most AVRs offer a microprocessor reset: a button combination listed in the manual that clears the working state without a full factory wipe. Try that before a factory reset, because the factory reset erases calibration, speaker settings, network and everything else you spent an evening on.
Settings truly gone is the second situation. Modern AVRs hold their configuration in non-volatile memory, so a clean power cut should not erase anything. What does corrupt memory is the surge or brownout at the moment power is restored, which in many Indian buildings is not a clean event. That is one more argument for a proper surge protector on the AV circuit, ahead of any argument about cable quality.
Prevention that costs nothing: after any full calibration, save or export the configuration if your model supports it (many current AVRs can back up to USB or to the cloud through the app), and photograph the key menu screens: speaker sizes, crossovers, levels, distances, input assignments. That turns a worst-case reset from an evening's work into twenty minutes. Your phone gallery is a perfectly good backup system; it just needs to know it has the job.
Pattern to watch: settings vanishing repeatedly without any power event. That is a service flag, not bad luck, and I would raise it with the authorised service centre rather than living with it.
If you get stuck restoring, tell us the model and what the display shows and we can walk you through it over WhatsApp.
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