The Wing Fossil is 1 of the translated names that was given to what English players of the Pokémon games know as the Plume Fossil.
in the nacrene gym
Take it to the museum in Nacrene City
To the left of the main entrance there is a female camperwho you have to beat in battle. When she asks you what fossil you want, choose "Plume Fossil".
you go to the museum section in lenora's gym and talk to the first person on the right then you give the person your fossil and she will bring it back as a Pokemon
You take the Dome fossil rather than the Plume fossil, when offered a choice of one or the other at Twist Mountain.
Unfortunately you can't. You can only get one fossil in the game, you have to trade for the other fossil, or the other pokemon.
The cover fossil is the Pokemon Tirtouga - a Water/Rock-type Pokemon and #070 in the Unova region.
What's a skull fossil
in the nacrene gym
yes
Take it to the museum in Nacrene City
fossil in relic castle
Almost any fossil can be received from the worker after the old amber, you just happened to get that first. He will give away a random fossil every day except for the new bird and turtle fossil Pokemon.
you can't get a wing set but on one of the bridges there are shadows. if step on one it might be a wing.
You need to go to relic castle and the backpacker will give you a Tirtouga or Archen fossil.
To get fossil pokemon go to the Nacreen Museum and talk to the people right inside the door. One of them takes you fossils and turns them back into pokemon.
Yes, in Twist Mountain, a man will give you fossils for the Gen I -> IV fossil pokemon. It is possible he will give you a Skull Fossil.