I am wondering if there is a difference between the answers of these when getting the volume of solid of revolution:
Region bounded by $y = x$, $x = 0$ and $y = 15$, rotated about the $x-axis$
Region bounded by $y = x$, $x = 0$ and $y = 15$, rotated about the $y-axis$
I tried the first one which is rotated about the x-axis and I got $2250π$.
For the second one I am confused on how to solve, is it possible that I use any of disk, washer, or shell method?

No objects are not the same.
However, you should be able to see the relation between their volumes.