iATKOS | United Kingdom

i need help. so recently I downloaded Big Sur on my old MacBook the wasn’t supported which was running fine, but then it kept asking me to update to macOS Tahoe, which obviously I didn’t. But I also had the official app to download macOS sequoia so my stupid self did that and downloaded it. I wake up and I see it. It isn’t showing me the setup wizard it’s just on the Lock Screen and it’s frozen and all I see is sequoia trees, and the only thing that works is the time and the password thing blinking. So can someone please tell me how to go back to El Capitan, also the recovery thing doesn’t work it shows me a few options but none of them do anything so pls help