Divisibility of 8 : if the last 3 digits are divisible by 8, then number is divisible by 8.
6y2 is completely divisible by 8.
By trial and error method:
If y=1,
612 / 8 = 76.5 (not divisible)
If y=2,
622 / 8 = 77.7 (not divisible)
If y=3,
632 / 8 = 79 (divisible)
Therefore smallest possible value of y=3