Also, be wary of the "Infinite Rings" hacks. Sure, it’s fun to be invincible for 30 seconds, but it ruins the rhythm. Sonic is about momentum. If you can’t die, the speed loses its meaning. Looking up Sonic the Hedgehog 1 unblocked is a nostalgia loop. You aren't looking for the best way to play the game; you're looking for the most convenient way to reclaim a sliver of your childhood while pretending to pay attention to a spreadsheet.
Legit browser emulators run the game right there in the HTML5 canvas. If a site asks you to download an ".exe" file to play Sonic, close the tab immediately. You’re looking for a ROM running in a Javascript emulator, not a virus.
Stay fast, and watch for the spikes.