What Comes Once, Twice and Never

Can you name the four days of the week that begin with letter "T"

What five-letter word becomes shorter if you add two letters to it?

You can see me on trees. My body is round and yellow.

I am very healthy. You can squeeze me and drink me in summer.

I taste sour.

Who I am?

I am a pet. I like mice.

I have nine lives. I purr and meow.

Who I am?

I am the third planet from the sun. I orbited by one moon.

I am also called as the blue planet and the living planet.

Who am I?