I think you need win bcc with a flying poke to win beedrill mega stone
If you lose 10 times with starter mega quest, that starter cant be used again for that , but if the starter evolves in the quest can wait 10 more losses (torchic 10 losses, combusken 20 losses and blaziken 30 losses)
For ampharos mega quest need:
strong poke (magnemite)
non afected ground poke (levitate or flying)
non afected water poke (chinchou water absorb or helioptile dry skin)
non afected grass poke (blitzzle sap sipper)
non afected dragon poke (fairy tipe)
non afected electric poke (pikachu with Lightning Rod)
And do a battle without mold braker and ground tipes
:3