Brain Teasers and Puzzles 

Workings

Hint
Oval becomes Opal.

Answers
Paperweight.
opal past spin melt wren swab mess find aged shed stay

Workings

Hint
Something's wrong with the letter O, and the word 'oifoeront' is important to the answer.

Answer
15 different letters: acdefhilmrstvwy.

Reasoning
The sentences should read:

As you can see, my printer replaces every third letter with the letter 'o'.

How many different letters have been replaced?

Workings

Hint
How many squares of size 1 x 1 are there?

Answer
There are 116 squares without a rook.

Reasoning
There are 61 squares of size 1 x 1.
There are 37 squares of size 2 x 2.
There are 15 squares of size 3 x 3.
There are  3 squares of size 4 x 4.

Giving a total of 61 + 37 + 15 + 3 = 116 squares.

Workings

Hint
The country spans more than one word.

Answer
Malta.

Welsh horses are my favourite aniMAL. TApir, llama, marmoset, and elephant closely follow. I don't care much for English rabbits nor ocelots, adders, goldfish, and spaniels.