Q1: Have I ever removed or edited a reference and/or saying because it's "too old" for my audience?
A1: Since I don't write YA, NA, or anything remotely related to children, "too old for my audience" is not a problem I have. "Too Young for Me" is something of which I am aware (you will never find the word "bae" in my work. Nope. I'm too damn old.)
Q2: Have I ever removed or edited a reference and/or saying because it's "too old" for my character(s)?
A2: Not so much for age as for the appropriate level of formality. This is particularly true in writing High Fantasy, less true when writing Contemporary Fantasy rooted in Western culture.
Q3: Have I ever removed or edited a Brand Name because it's "too old" for the story?
A3: In my Urban Fantasies? Yes. I try to never include Brand Names because what's popular today is riddled in ignominy tomorrow and out of business the day after, BUT sometimes they sneak in there. (I'm lookin' at you Lucite, Hakey Sack, and Frisbee).
Q4: Have I ever removed or edited a piece of technology because it's "too old" for the story?
A4: In Contemporary Fantasy? All. The. Time. I try to stay current on our constantly evolving technologies so as not to overly date a character who's supposed to be on-trend. It's little things that wave the "Get Off My Lawn" flag. Nobody "flips open their phones" anymore, and "swiping" means more than stealing these days. And thank gods for smartwatches and projection keypads because now my protagonist who wears form-fitting dresses can stop stuffing her phone in her bra.
Q5: Have I ever removed or edited a reference because it's "too obscure" for the audience?
A5: Rarely do I remove it. When I do, it's usually because it's part of a joke that's falling flat for all my pre-print readers. Otherwise, obscure references are fun little Easter eggs to drop that'll give an extra grin for anyone who gets the reference but by no means detracts from the narrative for anyone who doesn't get it. I love to drop Easter eggs. I am that girl. Not apologizing.