WORK ON A COPY OF YOUR DATA
Insert a column next to your questions
Next to the first question enter a 1, then move down one cell and enter a 3
Select the two cells, then double-click on the small black square at the
bottom right of the cell containing the 3. You should end up with the
questions all numbered from 1 to 600+.
Immediately below the last number enter a 2 and in the cell below that enter
a 4.
Select the 2 cells and this time DRAG the little black square down until you
reach 1 number higher than the highest of the first set of numbers
Now select the 1 at the top of the column and Data>Sort
You'll end up with a blank row between each of the questions