What does this rebus mean?

O
N
C
E
TIME

I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?

Without looking at a calendar, within a minute name, a boy's name using 5 consecutive 1st letters of 5 consecutive months

In the city of Brain Teasers, 5% of people do not list their phone numbers. Now if we select random 100 people from the phone directory, then how many people selected will have unlisted phone numbers?

Sally lives in a place where six months of the year is mild summer and the temperature drops significantly the other six months. She owns a lake where there is a small island. She wants to build a house on the island and needs to get materials there. She doesn’t have a boat, plane, or anything to transport them to the island. How does Sally solve this problem?

Find the last number in the series below:

voN luJ yaM raM ---

What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?

Identify the hidden meaning behind this picture?

Count the number of triangles in the below picture?

How far can you walk into the woods?