Zendesk Chat - Pin message / HTML message / Deploying app

Is there a possibility to pin message in Zendesk chat? Purpose is that custom survey link needs to be always visible to user on chat. Something similar like Zendesk default rating form.

Another question - can we post in chat some html code with styles? I tried it, and it only renders as text. I know about SDK for inserting components such as buttons is chat, but is it possible without SDK?

Last question - is there a way to test secure settings without upgrading plan to professional? Uploading app as private app first (only to test secure settings), before deploying it to marketplace.