Can you solve the below tricky visual equation?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

What has no start, end, or centre?

Spot 5 differences in two Christmas tree below:

Luis Garavito killed Density x Volume.

Who is Luis Garavito ?

Decode below three cipher riddles:

26 L of the A
7 D of the W
1000 Y in a M

Sachin bought a car with a strange 5 digit numbered plate.The water image of the number is 78633 more than my car number. All the digits of car number are distinct.

What is the original number on number plate?

As a whole I am both
safe and secure.

Behead me and I become
a place of meeting.

Behead me again and I am
the partner of ready.

Restore me, and I become
the domain of beasts.

What am I?

You are on your way to visit your Friend, who lives at the end of the hill. It is his birthday, and you want to give him the cakes you have made. Between your house and his house, you have to cross 5 bridges, and as it goes in the land of make believe, there is a troll under every bridge! Each troll, quite rightly, insists that you pay a troll toll. Before you can cross their bridge, you have to give them half of the cakes you are carrying, but as they are kind trolls, they each give you back a single cake. How many cakes do you have to leave home to make sure that you arrive at a friend's house with exactly two

Name a key which is hardest to turn.