These questions are often asked from a psychology perspective, where different generations will give unique answers based on their age/generation. As this is how I viewed your questions, I will answer this as someone born in 1992.

What age range is considered "middle-age"? Although the average lifespan varies, I like to believe most people will live to be 100, so my answer is 50.

What age range is considered "over the hill"? I think that is often a joke 60 year olds make at birthday parties while sipping on martinis. I hope NO ONE calls me "over the hill" at any age. So I do not consider anyone "over the hill" because I find it a rude thing to say.

What age range is considered "senior"? Depends on the venue. Most restaurants and cinemas consider 62-65 years old to be "senior status". In my opinion, I always think of 80 year olds as seniors. Or people with fully white hair, not just gray.

Is "over the hill" and "senior" the same thing? For me, "over the hill" means your grouchy about being old whereas seniors are more optimistic and often happily retired and happy in their little routines.

What are the age-based generation names (e.g., Generation X), and what years do they represent? I honestly don't know my own generation name, but I sure as hell do NOT consider myself a millennial! Millennials have such a bad reputation that I hate to be lumped in with that generation. I consider myself a "90s kid". That's my generation.