Having a No option that blocks registration doesn't make sense and would infuriate users. If they don't agree they just don't check the checkbox, which will block registration as you're wanting. Nearly every terms and conditions usage out there is the same usage we have implement, which is ideal as users are familiar with it and is the web standard.

For your usage it sounds like you need a middle-man page. For example you'd create a Joomla article that has your terms and conditions on it. At the bottom would be 2 buttons. 1 for "I Agree" and 1 for "I Disagree". Clicking "I Agree" would take you to CB registration. Clicking "I Disagree" would send you back to the home page. This usage is also another web standard (or software standard actually) that users are familiar with.

We would like to use also CB Connect plugin and let users create their account using FB etc... but I need them to accept privacy, terms etc... as soon as the app redirects them to the site (best would also be to ask them to accept privacy and terms soon as they click on the register with FB etc... but at moment I see that's not really possible)

Latest CB Connect works fine with terms and conditions in 1.9.1. It'll ask them to accept the terms on the incomplete registration page (assuming the global terms and conditions parameter is enabled). For CB 2.0 the new release of CB Connect will attempt to validate the internal registration, if it fails it'll pre-fill normal registration so the registration processes are not broken apart for the two user types.