can't we add alert box on some specific button, like alert box of "are you sure you want to play" on clicking play button

Answer 1

Yes, you can.
There are a few ways to do this, depending on where you want the script to sit.
https://www.w3schools.com/jsref/met_win_alert.asp
Remember that you can't format an alert box, so you if that's something you want to be able to do, look into modals instead. Search engines are your friend.

Answer 2

i checked your link but didn't found anything :(