Web SIP client requirements and settings for FreePBX

I wish to know the requirements to make SIP client in my Web application..

I am using FreePBX 14.0.1 version, for that FreePBX I had implement the Android SIP client, it works good. I had created chan_sip extensions in FreePBX.

I had the following doubts, 1.Is FreePBX needs ssl / tls certificate for the Web client? Is it mandatory? 2.Is any additional configuration needed for Web SIP client extension? Or the previously created extensions are enough , which are working on my android through UDP protocol. 3.To create the ssl / tls certificate, is FreePBX needs the public reachable host name? Or it will work with the self-signed certificate on LAN network?

Please clarify my above doubts and other than that if any additional settings needed for the Web SIP client? Guide me to start with this.