I think that "What's that castle's name?" should be considered a right answer
Indeed, it has been accepted for at least a year. It may have been added after your report, we cannot tell now.
We translate by the most common form here. Otherwise you could still argue that jmenuje is active nad called passive and that je pojmenován is even closer...
No, tamten is enough. Or even just ten. Note that it is not an adjective, but a demonstrative (pronoun).