The 8 gates are known and it's likely Yamato being an ANBU would know about them. Guy is after all Konoha's Thai juts specialist. That can still be resolved but as OP pointed out the limit of Kamui wouldn't be known by Konan unless there was a battle which forced Tobi to use it. You'd think with Tobi being a key character they'd do a better job explaining the how instead of flash back to Konan's younger days.
Sorry but you guys are just hating on the poor woman.
First of all Konan has been Tobidara's trusted ally longer than anyone in the series except for Zetsu. Tobidara trusted them so much that he couldn't believe that Nagato and Konan had betrayed Akatsuki, more specifically, had betrayed him.
Secondly Konan is Akatsuki's second best spy behind only Zetsu. (I'm not talking about having a spy network like Jiraiya and Sasori, I'm talking about being the actual spy and having abilities specifically suited for that kind of thing).
There is no way that you can convince me Konan, in all those years working with Tobidara and being such a good spy could not have been evaluating Tobi's abilities.
Finally, Tobidara is the one who showed Nagato to use the six paths jutsu, this implies that they would have trained together and obviously if they did then Konan would have been there and Tobidara would have used his abilities in front of her.