@SamiiHey Sami, thanks for your question here. 

The Digital Messaging team will be releasing a 'Special Notice' text feature soon in the Web Messaging widget. This will allow you to configure disclaimer text which will sit at the top of the Web Messaging widget and will be pinned to the top rather than in-line on the chat conversation. We expect this to be released in the next 2 weeks, and will be under the SaaS model for Digital Messaging, so no upgrades required. The only adoption steps needed will be configured in the Digital Messaging Manager portal. I will follow up on this thread once we've released it, and feel free to follow our "What's New" article for Digital Messaging here - https://docs.pega.com/bundle/platform/page/platform/release-notes/conversational-channels/whats-new-digital-messaging.html

For the second part of your question, you can configure the 'Welcome Message' in the Digital Messaging interface to be a Menu reply with two buttons for a 'Yes or No' in regards to what the disclaimer states. The payload of either reply can then influence the bots conversational flow behavior to progress in the conversation or not. 
 

Let me know if you have any additional questions here!