What does below chemistry rebus means?

What has a bottom at the top?

What's the best place to go shopping in the ocean?

Christina is practising her dance steps along with her friends. In a particular sequence, all of them form a row. At that point, Niharika is standing in the 4th position from either end of the row.
Can you find out how many girls are practising together?

Which alphabet letter is a question?

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

While handling a project, the landscaper is asked by the owner of the mansion that he wants four trees in front of his mansion that are exactly equidistant from each other.

How will he do it?

Replace the question mark with the correct number, given the pair of numbers exhibits a similar relationship?

? : 3839 :: 11 : 1209

You see a boat filled with people, yet there isn’t a single person on board. How is that possible?

The doctor advised his patient to take a tablet after every fifteen minutes. He gave him five tablets in total.

How much time will he take to have all the five tablets?