Is the largest rock in the world in Niger Africa?

Answer 1

No. Both the largest and the second-largest free-standing rocks in the world are in Australia.
The largest rock in the world is commonly, but erroneously, thought to be Uluru, formerly known as Ayers Rock. The largest rock in the whole world is Mt Augustus (Burringurrah, as it is known by Wajarri Yamatji traditional owners), in Western Australia, located inland, east of Carnarvon, and about 850km north of Perth. It is more than twice the size of Ayers Rock. It rises 717 metres above the stony desert, and extends for a length of 8km - almost the entire circumference of Uluru.