How to open specific contact chat screen in various popular chat/social-networks apps?
<h2>Background</h2>

<p>I've found that there is a way to open a specific contact conversation screen on WhatsApp, <a href="https://stackoverflow.com/q/16121163/878126"><strong>here</strong></a> .</p>

<p>Not only that, but I've found that an app called "<a href="https://play.google.com/store/apps/details?id=mobi.drupe.app&amp;hl=en" rel="nofollow noreferrer"><strong>Drupe</strong></a>" does the same, and maybe even more :</p>

<p><a href="https://lh3.googleusercontent.com/EQrs1jplMlP8SkOTdpqT4NzmgzGa5Wz2qageG1Pkjc6rKg0HBb-rwlOVW07_G7bAWgo=h900" rel="nofollow noreferrer">https://lh3.googleusercontent.com/EQrs1jplMlP8SkOTdpqT4NzmgzGa5Wz2qageG1Pkjc6rKg0HBb-rwlOVW07_G7bAWgo=h900</a></p>

<h2>The problem</h2>

<p>I can't find any official API of opening it this way, so I'm not sure how safe it is.</p>

<p>I've found SDKs, but not intents instructions.</p>

<h2>The questions</h2>

<p>I'd like to know more about what's available for various social-networks and chatting apps :</p>

<ul>
<li>WhatsApp</li>
<li>Facebook Messenger</li>
<li>Viber</li>
<li>Line</li>
<li>Telegram</li>
<li>Hangouts</li>
</ul>

<p>Possible features may be:</p>

<ul>
<li>open the conversation of a contact, when input is his phone number</li>
<li>have a new text that will be ready to be sent in the new screen</li>
<li>for Facebook, maybe also be able to open using the Facebook-ID of the person (meaning this is the input), instead of a phone number.</li>
</ul>

<p>Are such features available for each of those social networks and chatting apps?</p>