If I press alt+tab while currently doing a speedrun and then press alt+tab again to get back to it, does that invalidate it? It's only for about 1 second.

that's generally fine, depending on when you do so. if you have a video example, feel free to dm a moderator so we can see. i'd also recommend using a capture method that doesn't cut away from the game when you do alt+tab, but it's not strictly required