No, not even with a Y cable.
Standard USB ports do not supply the 12V needed to power a standard desktop drive. A Y cable will allow for higher amperage, but still at 5 V.
There is, technically a USB-PD (power delivery specification), but I am not aware of that implemented in any desktop computers or external enclosures.
This isn't 100% correct. you could always include a 5V to 12V switching supply in there, it's the power limit.
The most power you can get out of a "standard" USB 2.0 port is 2.5 (5 for 2 ports) watts (10W (?) on change ports) and the spin up power, even on a "green" drive, is more than that. With a changing port, you could do this, but then you'd have to say that, and few devices have that. You could add some kind of power storage to get the spin up done, but that would add up to to many issues/$$$. You might be able to do this with 2 3.0 ports (4.5W/port) but you would still have to limit the drive selections, and still require 2 ports.
If they ever come out with the new high power ports (up to 100W), then you could. (these make sure the requesting device can handle the spec, then up the 5V line to 20+ volts) (ASUS tables (others???) do this on their changer)