If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

Alpha is Beta's sister.

Gamma is a Beta mother.

Delta is Gamma's father.

Tango is Delta's mother.

Then,

How is Alpha related to Delta?

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

I travel all around the world but always stay in the corner. What am I?

Queen Elizabeth organised a royal party.

To Avoid uninvited guest royal family set a password.
Jack (an uninvited person) plan to enter the party. He stand nearby the door.

First guest comes, the security person said 'twelve' and guest replied with six.
Second guest comes , the security person said 'six' and guest replied with 'three'.

Jack thought is enough and he walked to the entry point. The security person said 'eight' , Jack replied smilingly 'four'.
He was immediately thrown out of the party. why ?

Can you find out which options fits best with the missing column?

I am a ten letters word
The first four letters have the power to rule,
Next, four-letter can be eaten.
The next three-letter represents a lady.
I can fly as well

what am I looking for?

Is the statement valid that it does not matter how much older a sibling is, eventually the younger one will be half as old as the older one?

He does not have any heart but still, He manages to live.
If you kill him, you will eventually die but yet you kill him.
He cannot run, who is He?

They came out at night, without being called.
They lost at day, without being stolen.
Who are they?