[SOLVED] What will happened if i put my stereo headset in 7.1 audio jack?

Solution
You use the splitter cable that comes with the headset. The green jack (marked with a headphone icon) goes in the green connector (stereo out), and the orange jack (marked with a mic icon) goes in the pink connector (microphone in).
What will happened if i put my stereo headset in 7.1 audio jack?
What is 7.1 audio jack? Did you mean optical audio? Or digital coax audio?
Nothing will happen. They are not compatible with 3.5mm audio connector.

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Depends on how those jacks are configured, could be nothing, could be you will get only partial audio meant for that channel. If you are worried about opening a worm hole into another dimension or causing your bed to catch on fire, that won't happen.
If i bought this motherboard ASROCK B450M STEEL LEGEND https://www.asrock.com/MB/AMD/B450M Steel Legend/
in which jack should I put this headset Cooler Master MH630