No.
No, because the model is user-based, not GPT-based.
It’s possible some users may still be on gpt-4-turbo, but I expect all or very nearly all are already using gpt-4o.
You can check for yourself which model is being run in your own conversations by checking the network log in Chrome DevTools while interacting with the GPT.
First open DevTools, click on the Network tab and filter by Fetch/XHR, then send your GPT a any message.
You’ll see an entry called conversation appear.
Click on conversation then open the EventStream tab, and you’ll see the list of message streams, right click on any with the role of assistant and select Copy message.
Then you can paste this message into any text editor and just read through it, but since I don’t like reading through unformatted JSON myself, I just put it into https://jsonformatter.org/ and look for the model_slug entry,
Which you can see here for me is gpt-4o.