Which conjugation of "ser" means "we are"?

Which is the "tú" form of "ser"?

Which is the "she" form of "estar"?

If I am describing Katy Perry, which version of "ser" should I use?

If I am describing me and my family, which version of "estar" should I use?

If I am saying "The students in this class are awesome", which version of "ser" should I use?