What has many keys but can’t open a single lock?

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?

How many times can you subtract the number 5 from 25?

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

What jumps when it walks and sits when it stands?

Can you spot what's wrong with the following sentence?

PETER WAS ANGRY AT
HIMSELF BECAUSE HE
ACCIDENTALLY LEFT THE
THE KEYS TO HIS CAR
AT HIS FRIEND'S HOUSE.

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

You knock a Table over in the library, and suddenly 20 eyes are looking at you.

I have an eye but still cannot see.

Who am I?