When I selected Chatgpt-4o-mini model, and tested the app, asking which model it is. It's telling me it is chatgpt 3. Which is not what I selected during the setup?
Has anybody got the same issue? Is there any fix going to happen for this?
Which OpenAI plan are you signed up for with OpenAI. Do you have active credits?
If you're on a paid ChatGPT plan (Plus, Pro, Team, or Enterprise), you can switch between models with the model selector. Perhaps you have different plan and can not switch? 
I've credits of around $9 there on api usage. I'm not on any paid plan though. But I'm able to choose between different models there and i selected the 4o-mini model there.
Not on a paid plan 
So you have a different plan (free) and can not switch so you do not actually switch.
You might read https://help.openai.com/en/articles/7864572-what-is-the-chatgpt-model-selector
Why not ask ChatGPT on their site?