Riddles about letters

I am the beginning of the end, and the end of time and space. I am essential to creation, and I surround every place.

I am the biggest alphabet, as I contain the most water in the world. Who am I?

What starts with "P" and ends with "E" and has more than 1000 letters?

I’m the end of the colourful rainbow. What am I?

The beginning of eternity, The end of time and space. The beginning of every end, And the end of every place.

What part of London is in Brazil?

While I am in air, I am not in oxygen. I am also in water, but not in hydrogen. I am necessary in all animals, but you won't find me in the zoo. Look in all brains and you'll find me there too. What am I?

What has five eyes, but cannot see?

Alone I am 24th, with a friend I am 20. Another friend and I am unclean. What am I?