"The candle fell and a fire started."
Translation:Thit an choinneal agus thosaigh tine.
"thosaíodh" would be the past habitual, but "tosaíodh" is past tense autonomous/passive person, so "tosaíodh tine" would be "a fire was started", which would seem to me to be equivalent to "a fire started" in english. Imerative would be "tosaigh tine" = "start a fire", wouldn't it. I did see (after posting this) a comment on another thread that "thosaigh tine" can be used intransitively, so used that way "thosaigh tine" would seem correct for "a fire started". I wasn't familiar with this usage.
Depends which letter. I've noticed that missing a single letter off usually gets allowed as a typo unless you correctly spell a different word by accident.
On the other hand it usually lets you off missing the initial mutations off words in Irish because "it's just one letter", and in that case I kind of feel that it shouldn't since they're such an important concept to learn.