1
I have heard that Imam Mahdi (AS) will bring the original Quran. Will this Quran be the final sermon by God?
The Quran which is present now, is the original Quran for all Muslims. The Quran which Imam Mahdi (AS) will bring with him is the one which was compiled by Hazrat Ali (AS) that was compiled as per the order/timeline of revelations, and nothing more. Therefore, Imam Mahdi (AS) will not bring any new Quran or any new Ahkam (Commandments) with him – Allah forbid!
2
I moved to Canada and bought a Condo. At that time I used magnetic compass to found Qibla direction and offered prayer for almost more than 7 years. Now I figured out that direction is wrong and found correct direction. In the same time I offered Qada prayer for my father too. Please let me know about those prayers?
If there was slight deviation i.e. you offered prayers slightly towards the right or left of the actual direction of qibla, then the offered prayers are valid inshAllah. And if there was a major deviation i.e. you offered prayers with your back towards the qibla, then those prayers are invalid and they must be offered again. And Allah Knows the Best!