I think it would be helpful to have both the male and female nouns as options in some of these questions.
Why is it not "Mae'r athrawes mynd i'r adre?"
Firstly any conjugated form of "Bod" needs "yn" to connect it to a verb-noun, noun or adjective. Secondly it is because "Adre" is an adverb which means "Homewards/To home" therefore doesn't need "i'r".
I put the male version and got corrected as 'Mae'r athro n mynd adre'.!