As an addendum to part 1 I'd like to suggest "Do not correct someone's terms for their family" to this list.
I'm adopted (from age 6), and in this case I was adopted by my grandparents. This sometimes made family connections a bit confusing as I use half from pre-adoption and half post.
For example, Grandparents are now parents, but their kids are my aunts and uncles, a habit I developed as a kid and referring to someone older than my mother as my brother felt weird.
Around age 11 I was chastised by someone at a party for calling my Aunt the "wrong" thing. She was very adamant that i was deliberately confusing people and that now I was adopted Aunt was now my sister and it was disrespectful to call her "just" an aunty. I remember getting very upset that i had upset my aunt and eventually being rescued by another guest.
Whether it's figuring out relationships in a complicated family adoption or whether someone was adopted outside their biological family and prefers to call their new family members something other than what is usual or even the "real" vs "biological" debate, leave them be, it's a personal choice and telling them how to think of their own family is simply rude.
I like this, and totally agree with you. My parents adopted my brother's child when she was 4, but had legal guardianship since 16 months, and had actually had the baby since birth, her birth mother living with them for the firs 8 weeks of her life. Until the adoption, she called them Nana and Papa, and I was referred to as Aunt Katie. Other sibs were also aunt/uncle, and Bro was Daddy. The day of the adoption my parents began referring to themselves as Mommy and Daddy and the birth parents by their first names. Ella now calls them exclusively mama and daddy (she is 9 now), the birth parents by their first names, and we are now her brothers and sisters. In fact, the family joke is now that her birth father is her brother from another mother.
Ella remembers her adoption day, and she knows that her parents were once her grandparents. She knows I was once her aunt, and who her birth parents are. She sees my brother frequently, her birth mom rarely. It is hard for my mom when people refer to her as Ella's grandma. She is Ella's mommy, and there have been people who continue to call her grandma even after correction. Not maliciously, I hope.