If it's discoverable in app, someone please fill in the details. But googling for the "Classic ChatGPT" leads to this link[1] which I have no way to verify was actually created by OpenAI and is described as "The latest version of GPT-4 with no additional capabilities."
So, buyer beware, but posting this link in case it does help someone.
So, buyer beware, but posting this link in case it does help someone.
[1] https://chat.openai.com/g/g-YyyyMT9XH-chatgpt-classic