Alpha starts with a vowel, so it isn't "A Alpha" it's "An Alpha."
Its when someone tries to convice you that they are better than you.
That depends on the context.
The difference between alpha and beta is small. The difference between alpha and omega is large. But I don't know the exact numbers.
Alpha is A
Beta is B
Alpha is also considered the dominant one in a family, group, pack, herd, etc...
If you have to ask you're not an Aldous Huxley fan.