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

I have an eye but still cannot see.

Who am I?

Name one eight-letter word with 'kst' in the middle, 'in' the beginning, 'and' at the end.?

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see?

Prove that the below maths equation is true.

8 + 8 = 91

There were two grandmothers and their two granddaughters.
There were two husbands and their two wives.
There were two fathers and their two daughters.
There were two mothers and their two sons.
There were two maidens and their two mothers.
There were two sisters and their two brothers.
Yet there are only six, who are buried here,
All are born legitimate and relationships clear.
How can this happen?

What is wrong in the below Picture?

At the local model boat club, four friends were talking about their boats.

There were a total of eight boats, two in each colour, red, green, blue and yellow. Each friend owned two boats. No friend had two boats of the same colour.

Alan didn't have a yellow boat. Brian didn't have a red boat but did have a green one. One of the friends had a yellow boat and a blue boat and another friend had a green boat and a blue boat. Charles had a yellow boat. Darren had a blue boat, but didn't have a green one.

Can you work out which friend had which coloured boats?

I come in different shapes and sizes.
Parts of me are curved, other parts are straight.
You can put me anywhere you like,
but there is only one right place for me.
What am I?

How can one talk without saying a single word?