Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

Can you complete the sequence puzzle?

AR TA GE CA LE VI LI _

Count the number of triangles in the below picture?

Find the number of squares in the below-given picture.

Find the 8 in the below-given Image.

If you remove one from eleven, it becomes ten. If you remove one from nine, it becomes ten.

How is this possible?

Assume the given figure to be a delicious doughnut. Yes, now you can concentrate more on the puzzle. So you have this delicious doughnut in your refrigerator when your friends come knocking at the door. There are eight of them. Now you have to make three cuts in this doughnut so that each one of you nine people can enjoy a piece of it. Neither you nor your friends would mind the size of their piece as long as they are getting it. How will you do it?

When I got four, I have it none.
When I got two, I have it some.
When I got none, I have it all.

What is it?

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see?

No matter how little or how much you use me, you change me every month. What am I?