question #1: hey Combat, why do you always type your text centered? Its a bit weird when you're trying to tell where the sentence starts from.
can confirm, I tested this on singleplayer (with /fill, but shouldnt be any different), the command is "/gamerule commandBlockOutput false".
however, you CAN NOT type commandBlockOutput as things like commandblockoutput, CommandBlockOutput, COmmandbLOCKouTPut etc. You MUST SPECIFICALLY type it as commandBlockOutput. (the pattern is simple, the first word doesnt have a capital letter, the other words do have capital letters)