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

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.

My thunder comes before the lightning; my lightning comes before clouds; my rain dries all the land it touches. What am I?

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

You enter your friend's room. He is not in his room. Although you see that on the bed there are two dogs, five cats, two giraffes and three pigs. Also, a couple of chickens and ducks are flying in the room.

Calculate the number of legs standing on the floor.

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

Can you name any English verb that becomes its past tense by simply rearranging the alphabets ?

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.

I am a seven-letter word but if you remove four of my letters I will have one left. What word am I?

If eleven plus two equals one, what does nine plus five equal?