Razor, Maser, Laser, Lover, Loner, Liver, Lager, Loser, Lader.
There isn't one.
resin rosin ricin
eager, ester, error
eager, ester, error
The five-letter word with three 'R's is "error." It fits the criteria by having three occurrences of the letter 'R' and consists of a total of five letters.
Queer is a five letter word.
Scarbeardearfeargearhearnearpearrearseartearwearyear.
appearbrotherchowderdrifteremperorflickerflustergrinderhoarderintegerjanitorlaundrymufflerneitherprinterremoverslenderteachervaulterwhisperyounger
biotic
The three-letter word for scull is "oar."
runners
certain