Does this mean "out of" "belongs to" "from (standing next to/near)" or all three?
Hmmm well it can be read as all three but it is possible to be more specific, e.g "Mae Megan yn dod 'allan' o'r tŷ." would be "Megan is coming 'out' of the house". Now I've never seen it used to mean "belongs to" when talking about a house but we do use it for a place e.g "Mae megan yn dod o Gymru", so it might be transferable to a house. Lastly to be more specific about "comes from being next to" you would say "Mae Megan yn dod oddi wrth y tŷ".