Answer 1

Yes.

&& , || are logical operators, works as compound conditional expressions..

&, | are bitwise logical operators works at bit level manipulations.

Answer 2

Anything , other than 0 value will be true in boolean equivalence. 0 means false.
So 2&&4 is true && true => true
true => 1 as integer value is the answer.

Answer 3

Use bitwise and operator & => a&b
printf("%d",a&b)

a&b => 0010 & 0100 = 0000
a&&b => 2&&4 => true && true = true