The least common multiple of two different prime numbers is the product of those two prime numbers.
Yes - if two numbers share no common factors (besides 1) the least common multiple will be the product of the numbers.
Never. The greatest common multiple of any two numbers is infinite.
Multiply any two numbers together. Their product will be a common multiple of the two.
If the prime factorizations have no numbers in common, the LCM is their product.
No, not always.