Ahh, so they're not actually looking for seniors then? Sounds like they want people who are "passionate" enough to spend months prepping for an interview so they can milk them dry without the risk of pesky things like "free time" and "family" getting in the way.
Tongue in cheek analysis aside:
- A phone interview to weed out timewasters.
- A RELEVANT technical take-home task that could be done feasibly in a few hours.
- A long, informal, in-person chat to determine "culture fit" and personality.
- Actually checking references.
That's all you need, anything more is just self-importance - or worse - time wasting.