What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

Considering the below equation:

V + II - VI = 10
IV - X + VIII = 20
IV - VII + VI = 30

Then, I + II + III = ?

Name a key which is hardest to turn.

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

In the four images below, can you find the odd one out?

Can you solve this picture maths equation?

What word begins and ends with an E, but has only one letter?

You are given four results as below:
1111 = F
2222 = E
3333 = T
Then, can you find out how to code 4444?

2 ladies and 2 girls need to cross a river in a boat big enough for 1 LADY or 2 girls. How do they do it?

A man is found dead in his bathroom naked with blood scattered all around him. The bathroom was locked from the inside and there is no trace of any struggle. There is nothing in the bathroom except his pant with the belt still around and his shirt. Also, the medic team can't find any incision in his body that may have been the reason behind so much blood loss.

The Police department is clueless regarding this murder mystery.
Can you?