When are you going to start new Great People Realm
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also, Beta v6 161 - this realm is old and your link is new realm ??
The realm of which b_mad gave you the link and the Beta v6 161 realm are the same realms. This realm, like all other beta realms, has started on September 24, 2013. There aren't any 'new' v6 realms that have started at a later date, it's also not known yet when new realms will be started.
... you should have possibility to register on that realm from the IO page where you select the world you want to log in
That, as shown below, is the way you should be able to join one of the v6 realms.
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Can I found somewhere the list of all ongoing realms ?
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No, we currently don't have a page that lists all the ongoing realms.