Answer 1

The or operator is meant to link two Boolean statements, not two potential answers in a Boolean statement.

something like if answer == 5 or answer == 6: would be what you're aiming for.

What you're encountering is a quirk where many languages will take a non-Boolean value where a Boolean is expected, and evaluate anything non-zero as true.

Answer 2

Your first test evaluates the following:
is input == 5;
is 6 == True.
And produces true if any of the conditions is met. Basically, it is always true, because any number that is not equal to 0 is considered to be True when converted into a boolean.

For your code to work, the if test should be written like this:
if input ==5 or input==6

Answer 3

you can do:
answer = input("What is the secret? ")
if answer == (5 or 6):
print("Correct!")
elif answer == 7:
print("Aren't we all secretive, then?")