Patterns and Sequences

The sequence is: 2, 4, 8, 16, ... . Kabir thinks the next number is 18, because it looks like 2 was added each time (2→4). His sister says this pattern is multiplying, not adding. Who is right?

The sequence is: 3, 6, 9, 15, 24, ... . Isha thinks this is an "add 3 every time" sequence, since 3, 6, 9 clearly shows +3. Her brother says looking further proves this wrong. Who is right?

In a code, each letter is replaced by its position in the English alphabet (A=1, B=2...). Coding "CAB", Rahul writes "3, 1, 2" and thinks this will always work correctly, whatever the word is. His friend says this only changes the letters, not what the word means. Who is right?

An arrow rotates 90 degrees clockwise each step: up, right, down, left, then up again... Priya thinks this cycle repeats every 3 steps. Her brother says it repeats every 4 steps. Who is right?