The Undertaker did not wrestle anyone at Wrestle Mania 6. His first Wrestle Mania was 8 and he versed Jake "The Snake" Roberts.
Shawn Michaels will face undertaker at wrestlemania XXVI
At WrestleMania 1, The Undertaker did not wrestle anyone. The Undertaker wasn't in a WrestleMania match until WrestleMania VII (7).
Kane
Edge
No one knows that yet, but at WrestleMania 27, Triple H will face Undertaker.
The Undertaker is coming back to WrestleMania 32 to face Sting and then retire the day after WrestleMania.
john cena
Shawn Michaels
Triple H
Randy Orton
Yes
He will beat HBK at wrestlemania 26