Frodo knows Gandalf because Gandalf was like Bilbo (Frodo's grand-uncle) guardian on Bilbo's adventures. Now, Frodo knows Gandalf through Bilbo.
Frodo is actually sitting a ways back in the cart from Gandalf, but because the seats they are on are not actually shown and compared, and the side of the cart is the same, the audience gets the effect that Frodo is just smaller, and not actually sitting back.
frodo bagins the hobbit FAMILY FEUD: frodo gandalf gollum legolas aragorn sam gimli
He made him leave the Shire with Frodo.
They were close to him, and knew that something was afoot, but not knowing what that was, they had Sam spy on him. (In the book) In the movies, they knew because Sam was roped into it without a choice by Gandalf, and Merry and Pipin knew only beause they ran into him, and desired to help when the saw that danger was following him.
Frodo did volunteer. It was Gandalf's belief that the ring chose him, and possibly knew it would destroy him to take it away. Also, Gandalf had a high regard for Hobbits, and that they could resist it's temptation longer than any of the other races, because of their lack of desire for power.
no
Frodo feels a sense of responsibility and fear after talking to Gandalf about having the ring in his possession. He realizes the weight of the task ahead and the danger that comes with it.
Frodo knew this ever since his talk with Gandalf at Bag End. Gandalf told Frodo of Gollum's history, and the sad fate of what happened to Sméagol and Déagol.
Frodo is actually sitting a ways back in the cart from Gandalf, but because the seats they are on are not actually shown and compared, and the side of the cart is the same, the audience gets the effect that Frodo is just smaller, and not actually sitting back.
frodo bagins the hobbit FAMILY FEUD: frodo gandalf gollum legolas aragorn sam gimli
Gandalf said it to Frodo
He made him leave the Shire with Frodo.
Gandalf tells him
They were close to him, and knew that something was afoot, but not knowing what that was, they had Sam spy on him. (In the book) In the movies, they knew because Sam was roped into it without a choice by Gandalf, and Merry and Pipin knew only beause they ran into him, and desired to help when the saw that danger was following him.
The group of people who set out from Rivendell with Frodo were; Sam, Merry, Pippin, Legolas, Aragorn, Boromir, Gimli and Gandalf.
Gandalf told Frodo about Gollum's history while they were at Bag End then later in the story Frodo told Gollum his true name.
Bilbo Baggins.Another opinion:Although Bilbo Baggins was Frodo's cousin (he is often assumed to be his uncle, but they are in fact cousins), and Bilbo named Frodo as his heir, I don't believe Bilbo was actually Frodo's guardian during the whole of Lord of the Rings. I think his actual guardian was Gandalf the Grey (later Gandalf the White) the wizard that had been friends with him since he was a child. While Bilbo spent his years in Rivendell writing a book, Gandalf was off helping Frodo to save the world, and doing the best he could to protect the young hobbit on his dangerous journey.A 3rd opinion:In the book, Bilbo was 78 years older than Frodo, and he adopted Frodo (age 12) when both of his parents died in a boating accident. Gandalf was an extremely infrequent visitor to the Shire. Gandalf and Frodo were together on the Quest for Mordor for a grand total of three months, and two of those months were spent at Rivendell with Bilbo. I vote for Bilbo as Frodo's guardian.