1) No.  2) No. You do have to have a working email address to send from (Email-to-SMS Gateway) or a Twilio account like in the extended cut.    3) Depends.  If you want to send a varying message each time you would have so have  a field in you form for you message.  If it is just a standard message then you could / would write it into the VBA.  4)  See reply for 3.  5) The message is sent from the customer form that is open in the example.  There would be other ways to send to multiple people but that would require some programming and VBA.

Be sure to watch the videos in the links - multiple times if needed.  Especially the Send Email. This isn't a quick plug and play type of thing.  You have to have some pretty solid foundation to understand how to tackle it.
In addition take a look at the Value From a Form video.  That would help you sending a message from your form text box. (Question 3 & 4)
  

Some telephone plans still charge for messaging.  Be careful, and offer some way to opt out of text messages.  You don't want to alienate a good customer if this is for a business.

FYI - From Google:
Is there a limit on text size?
        "The character limit for a single SMS message is technically 160 characters. However, most modern phones and networks support message concatenation: they split large messages into individual SMS messages (called "segments") and then re-create the large message at the receiving end."

The purpose of my video wasn't to show you how to send bulk-SMS messages. My goal was to just show you how to send one. If you want to learn how to send to a group of people, then I'd recommend learning how to program Recordsets. That would be the most efficient way, and I've covered them extensively in other videos.