1.Where did the Incas go? (No idea Spanish never knew of machu picchu) Conquered by the Spanish who systematically took their empire apart, combined with a smallpox epidemic gutted the population and infrastructure. Machu Picchu was abandoned before the Spanish arrived, most likely devastated by Small pox.
2.Why does the air shafts of the pyrimads line with the stars? (no idea) They don't (one of them curves and bends) and they didn't when the pyramids were built either as the alignment has changed, see also the Orion correlation myth.
3.Who built the statues on Easter island? And purpose? (No idea) The Easter Islanders' ancestors, who built them to celebrate/commemorate famous tribal chiefs.
4.Is there underground military bases in Antarctica? (Wouldn't surprise me) No bases underground only above ground and strictly non military, the US Army attempted underground bases in Greenland on glaciers but found the ice moved too much to make them feasible.
5.Was malloray the fist man to stand on the summit of everest? ( I have a gut feeling he was) Can never be proven, besides it might of been another unrecorded effort that succeeded.
6.What did happen at Roswell? (No idea) A balloon belonging to Project Mogul came now and the US intelligence services covered it up and then used Aliens to deflect coverage away from what they were doing.
7.What happened at the Dyatlov pass incident? (possibly military) A load of hikers died from exposure and hypothermia after an avalanche.
8. Did Oswalds bullet kill Kennedy? (Not sure but I believe he was involved.) Yes it did, the forensic evidence stacks up and 50 years since and collapse of the USSR no solid evidence, proof or whistle blower has come forward.
9.9/11 ? Was it planned in a cave? (Balls) It was Al Qaeda, but since that is a fragmented group as opposed to a rigid structured group it was unlikely to have been in a cave but someone who came up with a simple plan that got money from Bin Laden to carry it out. Devastatingly simple.
10.Who made the crystal skulls? (No idea) Modern day hoaxers and pranksters, none have proven to be anything other than a modern fake.
11.What is buried on Oak Island? Could it be the ark from the crusades? ( really fascinating

) Nothing, its all hype myth and idiots making evidence fit their preconceptions.
12.what's the purpose of the Nasca lines? (No idea) No one knows for sure as the Nazca didn't leave any written explanations of them. It is likely they are part of religious ceremonies to ensure the area got water from the mountains. They aren't UFO landing pads.