"Where did you eat yesterday?"
Translation:¿Dónde comiste ayer?
You need the accent for the ó, and you can use tú though it would be superfluous and you'd also need the accent over the ú.
Yes but ustedes is the polite form of you and takes the third person plural
A dónde is used for questions in future tense "¿a dónde vamos?" Where are we going?
Your answer should be correct too, «a dónde» is used to ask for directions or adresses.
My understanding of "a dónde" is that it is used when there is a plan to move towards somewhere/somtheing, which is not the case here.
Ok well how about mine didnt even say donde it said did you eat yesterday
This one is wrong, comieron would be they eat, third person plural, where did you eat is comiste o comió