Isn't it avo with the "circonflexe" on the o for grandmother? And this spelling for grandfther? Or are they interchangeble?
No, they are not. Avó - grandmother, avô - grandfather, vovó / vó - grandma, vovô / vô - grandpa, avós - grandparents.
Are both pronounced the same? If so, how do you know the difference in spoken language?
Vó = O like o in hot.
Vô = O like o in bold.
Paulo, você é o melhor. Obrigado.
Muito ùtil, obrigado :)
Do the avó/avô and vó/vô differ like it does in swedish where one of them is for the father side and the other for the mother side?
They are the same. "Vô" and "vó" would be "granma/grandpa" and their variations. For mother/father side, you should use "Materno" and "Paterno".