What is the Surname of Barbie Doll?

You have to put a letter on the following to make it a meaningful word. The only challenge is that you can't use 'E'.

S E Q U E N C _

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C

Two in a corner, one in a room, zero in a house, but one in a shelter. What is it?

What is the centre of gravity?

The answer I give is yes, but what I mean is no. What was the question?

In four steps you need to move the word 'cold' From 'warm' by replacing one alphabet at a time such that every word formed at each step is acceptable in English Dictionary.

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.

What does this simple rebus mean?

What does this rebus riddle means ?