Using Touch object for the buttons in the game.

Are your btnYes and btnNo objects of "Button" type? In this case don't use Touch events for them. Use btnYes -> On clicked event instead.

If they are sprites, change events to Touch-> On touched object. "On touched" is a triggered event, it's triggered only once, which is what you normally want for menu buttons, toolbars, settings icons etc.

"Is touching" is a continuous event, it's executed many times per second, while the finger is touching the object. You should use it for controls like a virtual joystick, firing button etc.

Yes, Button object under Form Controls. If you are using it, it has its own "On clicked" event which will also work on touch screen.

But there are many problems with form controls (for example it's quite hard to change their appearance), and in many games it's better and easier to make buttons with sprites or text objects instead.

By the way, you can easily test your game on touch screen of your phone using "Remote preview" option.

No! Simply start Remote Preview in Construct 3, it will give you a link, open that link on your phone. Takes 5 seconds.

Menu -> Project -> Remote preview.

But it doesn't work in free version.