I look at you, you look at me I raise my right, you raise your left. What am I?

There is one thing that goes round the house and also inside the house but never even share a brief touch. What is it?

What goes up but never comes down?

There are hundred red gems and hundred blue gems. The blue gems are priceless while the red gems equal wastage. You have two sacks one labeled Heads and the other Tails. You have to distribute the gems as you want in the two sacks. Then a coin will be flipped and you will be asked to pick up a gem randomly from the corresponding sacks.

How will you distribute the gems between the sacks so that the odds of picking a Blue gem are maximum?

What's a single-digit number with no value?

Forwards I am heavy, backward I am not. What am I?

You need to arrange three 7 and mathematical symbols to form number 1?

You along with your friend are standing in front of two houses. Each of those houses inhabits a family with two children.

Your friend tells you the below two facts:
1) On your left is a family that has a boy who likes accounts but the other child loves science.
2) On the right is a family with a seven-year-old boy and a newborn baby.

You ask him, "Does either of the family have a girl?"

To this, he replies, "I am not quite sure. But can you guess that? If you are right, I will give you $500."

Which family do you think is likely to have a girl?

When you say goodbye, I am what you need to tie.
I come as a couple and go wherever you run.
Who am I?

Replace the question mark with the correct number below.