Is it possible interact with my playcanvas application from an external html input?

i am planning to embed my play-canvas app to my already existing html page, but i want to know if the buttons which i have on my already existing html page can be made to interact with the play-canvas app i want to embed ?

Yes it is:

There are a few posts on the forum about this as well.

In fact you can use any of the UI frontend framework like React/Angular and use that compiled code inside playcanvas and have a very interactive application.

The most sadly thing is you can’t install it by npm or bower, currently.
So you your application can’t depend on playcanvas.