Yes, Sonic Frontiers intentionally reuses levels from previous games

digitaltrends.com:

During Gamescom, fans shared footage of the Cyberspace levels in Sonic Frontiers that featured similarities to levels from previous Sonic titles, such as the Windmill Isle in Sonic Unleashed. Now, Takashi Iizuka, head of Sonic Team, has confirmed that the similarities between Cyberspace and those classic levels are intentional.

In an interview with Eurogamer, Iizuka said that the Cyberspace levels are “digital expressions of the worlds in the memories of Sonic the Hedgehog.” In other words, they’re recreations of the memories of places that Sonic visited throughout his 30-year history, such as Green Hill Zone from Sonic the Hedgehog, Sky Sanctuary in Sonic 3, and even Radical Highway from Sonic Adventure 2. He even noted that some of those levels may get mixed together, as the Green Hill Zone Cyberspace level has the same level design as the Windmill Isle tutorial level from Unleashed.

it's the exact same level design#SonicFrontiers pic.twitter.com/3dwsGPmzrG

— Mikester (@mikesterp1) August 24, 2022

“We kind of want to reuse those memories — like the memories we have as well, because we played the games with Sonic — but the team is doing it intentionally, to kind of poke at those little points that players are going to pick up on immediately. Like, ‘I remember this exactly!'” Iizuka said. “And we are making levels that maybe look different, but feel the same as other things you have experienced. There’s going to be a mix of those very intentionally nostalgic or familiar areas, but there will also be some brand new things nobody’s ever seen before.”

Iizuka’s description of the Cyberspace levels is reminiscent of Kingdom Hearts: Chain of Memories. In the Game Boy Advanced game and the PS2 remaster, every floor in