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reachable=false means other node cannot connect to your node. But since getnetworkinfo return "network" with name "onion", that means your node already use Tor. Although if you want to configure your node to be reachable, you'll to perform additional configuration using guide which mentioned by @nc50lc.
Thank you very much, I don't know this moment that "getnetworkinfo return "network" with name "onion", that means your node already use Tor."
Now it’s clear that I need to raise a hidden service so that other onion peers can connect to me.
One more thank you very much