Could it also be "Akkor és oda" ?
"Oda" = "To(wards) there". In this sentence, "There" is meant as the location, so you simply use "Ott".
In fact it could be. 'You will go then and there as I say to you.'
Can't it be "akkor meg ott" as well?
Yes, it can.
Why not 'akkor pedig ott'?
then=aztán - miért nem jó?
Does this sentence mean the same of the English then and there (immediately), or literally then (at that moment) and there (at that place)?