A bus passes my house every hour.
Does (1) means that one the same bus passes?
No. "A bus" does not mean any particular bus, and in this construction, it does not necessarily imply the same bus.
One bus passes my house every hour.
Does (2) means that exactly one not necessarily the same bus passes?
Yes. It means that one and only one bus passes your house, but it does not necessarily mean that it's the same bus.
Some bus passes my house every hour.
Does (3) is equivalent to (2) or (3)?
(3) is of course equivalent to itself, so I assume you mean "(1) or (2)."
(3) has a somewhat different connotation than (1) and (2). It does connote that it's the same bus every time, but it also connotes that the speaker is unfamiliar with this bus. It's not any particular bus, it's just "some bus." The construction is also slightly informal, and it might be spoken in a tone of annoyance at this "some bus" that keeps passing the speaker's house. You might also see this written as "Some bus keeps passing my house every hour."
Buses pass my house every hour.
Does (4) means that one or more buses passes my house?
Yes.
Some buses pass my house every hour.
Does (5) is equivalent to (4)?
No. (5) means that, every hour, more than one bus passes your house. (4) could mean the same as (5), but it could also mean that one bus passes per hour. It's ambiguous.
What must I write if I want to mean "the same bus passes every hour"?
You should write "The same bus passes my house every hour," just as you put it already.
