Lyn writes:
"In all these sentences "being" is the present participle of "be" and means that the main verb or action is ongoing, or happening continuously at that time."
Unfortunately, the community tutor is wrong on both points. In fact, “being” is the gerund — a noun form of the verb. “To be” is used with the past / passive participle (“v3”) to form the passive voice. We could restate number 1 in the active voice:
We managed to climb the tree without anyone seeing us.