Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

How many triangles can you count in the figure given?

Living above a star, I do not burn
Eleven friends and they do not turn
I can just be visited in a sequence, not once or repeatedly
PQRS are my initials
Can you tell my name accurately?

You are an expert on paranormal activity and have been hired to locate a spirit haunting an old resort hotel. Strong signs indicate that the spirit lies behind one of four doors. The inscriptions on each door read as follows:

Door A: It's behind B or C
Door B: Its behind A or D
Door C: It's in here
Door D: It's not in here

Your psychic powers have told you three of the inscriptions are false, and one is true. Behind which door will you find the spirit?

Why is the longest human nose just 11 inches?

There are 2 sand hourglasses.

The small one can measure 5 hours and the large one can measure 7 hours.

How can we measure 16 hours with 2 sand hourglasses running together ?

Can you count the number of squares in the given picture?

What does this simple rebus mean?

Which alphabet letter is a question?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?