1) Many local town are adopting "exposed run" restriction, but that's a local Code issue, not one found in the NEC, as long as support requirements are met. My town started that a few years ago, limiting exposed runs of AC, MC & Greenfield to 24" from penetrations (except for motor and lighting whips). Most of the IL Lake Shore has already outlawed NM, so that's moot for us.
2) I've always installed one within L.O.S. of the HVAC in the basement - usually a lot less than 25'.
I've always heard the "25'" rule applied to roof mounted HVAC / mechanical stuff - so they wouldn't have to run extension cords from inside the building. (or to sign receptacles with adaptors)
