Yea, don and doña are also use in Puerto Rico for the elders, especially if they have no other title or if they’re in situations where they don’t use/want to use the title. I use it when I encounter elders!
It seems the use of señorita vs señora to call an unknown (to the speaker) woman varies by region/country. In some, I’ve heard señorita, in others, señora, without distinguishing between the ages of the women. Hence in some countries all unknown women are called señorita until marital status is known or real old age kicks in, when then it changes to señora and doña, respectively. In others, they use señora until the same conditions apply, and then make the switch.
And of course, if the title of the woman is known, then that is how she must be addressed and introduced as, unless she rejects it.