Does the walk in run always score?

[WestMichBlue]

Bases loaded, tie score, bottom of 7th, two outs. Batter is walked.

The rulebooks say that a run counts if it is scored before the 3rd out (with the obvious exceptions).

The assumption is that R1 is awarded home instantly and the game is over when all runners touch the next base. But I cannot find any rules that would justify that interpretation.

The question is: "can something happen that becomes the third out prior to R1 reaching home and thus nulify the winning run?"

Would it make a difference if this happened in the 3rd inning? Suppose R2 runs past 3rd base and is picked off by F2 before R1 touched home? Does the run count - and the inning end.

Rule reference or interpretation, please.

WMB