What does below chemistry rebus means?

I hide my treasure in the ground, my tail is big and fluffy. If you spot me in a tree, please don’t call me scruffy. What am I?

There was an aeroplane crash, every single person died, but two people survived. How is this possible?

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

Can you decipher these quotes by Albert Einstein?
Blf xzm mvevi hloev z kilyovn lm gsv ovevo lm dsrxs rg dzh xivzgvw.

It is a nine-letter word.
The exact opposite of the phrase "friendly and outgoing"
It contains the word "over".
It starts will a vowel.

What is it?

When a clock is observed, the hour hand is at a minute mark and the minutes hand is six minutes ahead of it.

When the clock is observed again after some time, the hour hand is precisely on a different minute mark and the minute hand is seven minutes ahead of it.

Can you calculate how much time has elapsed between the two observations?

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?