Seeing some tweets about how the #ObiWanKenobi series breaks canon based on what is said in A New Hope. So let's go to the source and break down the dialogue.
When the Falcon is pulled into the Death Star, Vader says: "I sense something... a presence I haven't felt since..."
He doesn't end that sentence, so we don't since when. He doesn't say 20 years ago, so him seeing Obi-Wan 9 years ago works.
Vader tells Tarkin: "A tremor in the Force. The last time I felt it was in the presence of my old master." Again no amount of time is given.
Tarkin says "Surely he must be dead by now," meaning the Empire never had confirmation of Obi-Wan's death.
Vader says he has been waiting for Obi-Wan. Originally we all thought he was waiting 19 years, but it's possible he was waiting actually 9 years. Siths are impatience any amount of time would make him say "at last." (Also he is just super dramatic).
Vader tells Obi-Wan when he left him he was the student but now he is the master.
Vader is talking about leaving Obi-Wan in ROTS. Remember he wasn't given the rank of Master. I highly doubt he will "leave" Obi-Wan in the series. Obi-Wan will most likely escape.
Leia is being formal because she is an envoy for her father. She isn't asking Obi-Wan a personal favor, she is asking him to be a general again and join the war.
Leia knowing him actually strengthens the reason her father gave her this job.
Leia doesn't ask who Ben is when Luke says his name, she actually jumps when she hears it.