After installed CB and CB Subscription in last joomla version is possible get 2 different registration forms for 2 different kind of clients

You mean by using CBSubs Plans? Yes and no. Yes, it's possible to limit specific fields to a specific subscription, but no it's not possible to have 2 entirely separate forms. You can have a plan hide fields on registration under the Workflows tab. You can also link to plans directly to have the illusion of 2 separate forms I suppose.

how can I reserve access to some pages and content to only paid subs?

Depends on the content. If it's Joomla articles you'd just use CBSubs Content and its built in content protection. You could assign them a special usergroup (see Access tab of your plan) and protect content using normal Joomla ACL. You could also use CBSubs Content and its By URL Part protection to protect a URL.

I want register for free everyone but the forms are different if the user is a person or is a business agency.
Who of them pay the premium subscription the person become, for example, from "registered" to "authors" and the agency from "Editor" to "Publisher".

That should be easy enough to do with your plans configured to assign those usergroups under the Access tab of your plans.

I hope to explain clear what I need, so is it possible?

Seams like it, yes. Feel free to try this all out on our demo site below.

demo.cbdemosites.com/