Has Bought or Had Bought?

You would say 'had' if you bought the book last year, but something happened that that situation is different now. It's in the past. I bought this book last year. I have bought this book in the last year/last twelve months.

Is has bought correct?

However, if you're simply stating a fact, most people would use the two interchangeably, and not consider either to be wrong (Though most grammarians would argue that the present perfect "have bought" is more correct.)

Had bought or had brought?

'Brought' is the past tense of bring. When you pronounce the word 'brought', listen for the 'r' sound after the 'b'. I brought my guitar along with me. 'Bought' is the past tense of 'buy'.