Question 1 :
Associativity has no role to play unless the precedence of operator is same.
Associativity is only needed when the operators in an expression have the same precedence. Usually + and - have the same precedence.
Consider the expression 7 - 4 + 2. The result could be either (7 - 4) + 2 = 5 or 7 - (4 + 2) = 1. The former result corresponds to the case when + and - are left-associative, the latter to when + and - are right-associative.
Usually the addition, subtraction, multiplication, and division operators are left-associative, while the exponentiation, assignment and conditional operators are right-associative. To prevent cases where operands would be associated with two operators, or no operator at all, operators with the same precedence must have the same associativity.
Question 2 :
The expression of the right hand side of || operators doesn't get evaluated if the left hand side determines the outcome.
Because, if a is non-zero then b will not be evaluated in the expression (a || b)
Question 3 :
In the expression a=b=5 the order of Assignment is NOT decided by Associativity of operators
The equal to = operator has Right-to-Left Associativity. So it assigns b=5 then a=b.
Question 4 :
Associativity of an operator is either Left to Right or Right to Left.
Yes, the associativity of an operator is either Left to Right or Right to Left.