What does the below rebus riddle means?

What does this rebus means ?

PROG WORKRESS

All of you like to eat me. I am a five-lettered word. Remove the first two and I turn into an infamous animal. Remove just the first and I become a heinous crime. Remove the first and the last and you can groove on me.

Can you guess who am I?

What is so fragile that saying its name breaks it?

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?

Solve The below Equation:

ALFA + BETA + GAMA = DELTA

Can you solve the below algebraic mathematical equation?

(J+O+I+N+T)3 = JOINT

John said, "If yesterday was tomorrow, today would be Friday."

When did John make this statement?

A man has eighty-one cows ( numbered 1,2,3...81 as such). The beauty is that cow no. 1 gives 1ltr of milk, cow no. 2 gives 2ltrs of milk and so on. The man wants to equally distribute the cows among his nine sons so that each one of them gets the same quantity of milk.

When I go in I might cause pain. I cause you to spit and ask you not to swallow. I can fill your hole. What am I?