I want to restrict model to download from network tab from developer menu as shown in video
It’s not possible. Moreover - securing assets that find their way onto a user PC really isn’t worth spending much time on. Browser has to download the model to display it - so it has to appear in that tab and will be, in one way or another, accessible for the user to download and save on their disc.
Then how do sites like sketchfab which allow you to preview their paid models protect the models from people?
you could check a referrer and, if it is not specified, which would be the case if you go directly to the model url, return a 403. unfortunately it is more like an inconvenience than a protection.