Kylo Ren has the ability to probe someone's mind with the Force. How does he know a power that Darth Vader didn't know? He needed a droid to probe Leia's mind.
Simple. Kylo knows some abilities that Vader doesn't. Considering he isn't a Sith and is from some other dark side line it isn't surprising he could do things the Sith couldn't.
Or Leia is capable of blocking such things which was actually mentioned in one of the earlier scripts.
Vader was able to figure out who Leia was, but couldn't read minds? I guess you could pretend he didn't and was just bullshitting, but I doubt it. Besides, Rey had zero training and was able to do it. It's more likely that Lucas didn't have the concept of the Force down at that point, and Disney doesn't care.
Who said those we're only his surface thoughts? Besides you, I mean. Thoughts go beyond what's just on the surface, and Vader slowly questioning him would only western any defenses he put up allowing him to prove deeper. And again, Retired
Rey's done it with zero training from Snoke.
Doesn't really address my question. Not seeing the word surface there.
Nothing she does without training is ask that impressive aside from this. Even in her duel with Kylo, the novel makes it clear she's using rage because she thought Finn was dead, she was still losing, even with Ren holding back.