Is it possible to copy something to the clipboard or paste from the clipboard in a project? Ex: Clicking a selected text would allow you to do something like copy(str)?
Nope 
But, if the user is using an external keyboard, and as long as there’s text in the clipboard, and as long as isKeyboardShowing() == true, pressing cmd+v will dump the contents of the clipboard into the keyboard buffer and also trigger keyboard(key).
Which isn’t at all the same thing, but… you know… it’s something worth knowing.
There’s an entry in the issue’s tracker for part of what you want.
https://bitbucket.org/TwoLivesLeft/core/issue/234/save-text-to-clipboard
Good to know. Thanks