NOTE: Make sure you have solved all puzzles on card 1 before proceeding with these.

Clue 1
One of the bits you decoded on the back of card 1 said 'locations.'
Clue 2
Where on Agatha's Facebook page are many locations referenced?
Solution
Checking the location tag for each profile pic, in order, will give you a message using the first letter of each. The plaintext is: "Key 3 is Beatle."
Clue 3
Looks like she's shared a lot of profile pics from different locations.

Clue 1
One of the bits on the back of card 1 translates to "Favorite quotes."
Clue 2
Have you found her favorite quotes in her Facebook info? They don't look like quotes to me...
Clue 4
Hmmm... Day, month, year... word?
Clue 3
They look like dates, only... with one extra set of numbers...
Solution
Using the modified Arnold cipher in her quotes to index, you can draw a single word out of each referenced quote. The result is: "The fourth key is Mercury."

Clue 1
One of the bits you decoded on the back of card 1 said 'locations.'
Clue 2
Where on Agatha's Facebook page are many locations referenced?
Solution
Checking the location tag for each profile pic, in order, will give you a message using the first letter of each. The plaintext is: "Key 3 is Beatle."
Clue 3
Looks like she's shared a lot of profile pics from different locations.

Clue 1
One of the bits you decoded on the back of card 1 said 'locations.'
Clue 2
Where on Agatha's Facebook page are many locations referenced?
Solution
Checking the location tag for each profile pic, in order, will give you a message using the first letter of each. The plaintext is: "Key 3 is Beatle."
Clue 3
Looks like she's shared a lot of profile pics from different locations.

Clue 1
One of the bits on the back of card 1 translates to "Favorite quotes."
Clue 2
Have you found her favorite quotes in her Facebook info? They don't look like quotes to me...
Clue 4
Hmmm... Day, month, year... word?
Clue 3
They look like dates, only... with one extra set of numbers...
Solution
Using the modified Arnold cipher in her quotes to index, you can draw a single word out of each referenced quote. The result is: "The fourth key is Mercury."

Clue 1
One of the bits you decoded on the back of card 1 said 'locations.'
Clue 2
Where on Agatha's Facebook page are many locations referenced?
Solution
Checking the location tag for each profile pic, in order, will give you a message using the first letter of each. The plaintext is: "Key 3 is Beatle."
Clue 3
Looks like she's shared a lot of profile pics from different locations.

Clue 1
By this point you'll have used almost everything...
Clue 2
Except for one item. If you haven't solved your cards fully, stop here until you do so.
Solution
The password to the final video, decoded from card 5, is: "Anaconda."
Clue 3
Anything you haven't used yet from card 5? Maybe something that could relate to the Ouroboros?