If brake pad worn out, still can brake or totally become brakeless?

The best solution for this is to check them regularly at every oil change.

They are not going to suddenly wear out unless there is an issue which you will know because the brakes will be dragging and you will feel it.

When they wear out, they will start making noise but still operate. Eventually they will be grinding and that will tell you that you need to get them changed immediately.

Here is a guide that will help with this:

https://www.2carpros.com/articles/how-to-replace-front-brake-pads-and-rotors-fwd

https://www.2carpros.com/articles/how-to-replace-rear-brake-pads-and-rotors

Below you will find the process from the manual on how to do replace them as well.

Let us know if you have any questions. Thanks