Oh, I thought you hop glitched through the whole level. It's surprising that it only takes two hops at the end to make a 361 happen. Knowing this, I would say it would be possible to replicate again for a run if given enough tries.
Now I think we should do Ending 4 for sure: it's the coolest and the fastest. ;) Thanks for voting everyone. I have made videos for almost every beginning, so I will post a link to a playlist for all the beginnings, and you can vote on those too.
EDIT: I did some testing on Mario's running speed with all this hop glitch talk. I made a
handy little graph (click on it to make it bigger) for a nice visual representation of Mario's speed. The graph covers the period of time, frame by frame, that it takes Mario to go from a dead stop to a full run. I used frame advance and recorded Mario's speed value at every frame. As you can see, the first section of the graph (from frames 0 to about 25) is not a straight line. When Mario is accelerating, his speed goes up by one then two then one then two (ex: 0,1,3,4,6,7,9,10). For some reason, Mario's acceleration tops out at the 35-37 range for about 55 frames before Mario accelerates further. This top out at the 35-37 range follows the same oscillations as a full run. This oscillation is: 47,48,47,49,48,47,48,47,49, etc. I also tested out flying speed oscillation, which is much more linear with the following pattern (only applies when holding forward): 51,50,49,48,47,51,50,49,48,47,51, etc. This means if you get unlucky with fast flying, it may be slower than running.
EDIT 2: Yay! I just got a 361 as well! It's definately replicable if you get good enough at it. I did the same thing as you skamastaG: made a long jump to the green pipe, released forward in midair, jumped off the yellow blocks, and jumped off the ground and into the goal. I think we can do this in a run!
EDIT 3: I just got 361 11 more times! It's just luck of what the oscillation stops at, I've gotten much better at touching the ground for only one frame at a time (yes at 100% speed). :)