If someone’s given Hebrew name is for example Avraham but everybody calls/called him Avrum – which name should be used for mishaberach lecholim it for yehrtzeit, or for that matter I on a matzevah? Thank you.
His correct Hebrew name should be used for everything, as this is his real name. It is very common for people the be called with a name that is sightly different than their correct name, or to be called be only one of their names. Nevertheless their correct name is what should be used for these things.