re: instagram/phone
My youngest is 12. Doesn't have a phone (although we do have an 'emergency' phone that we allow her to take for after school activities or when she goes to friends houses, etc...)
Pro tip - if she wants an instagram account, is responsible, gets good grades, not in trouble, it's an easy passive reward to allow (and take away if things go sour).
Pro tip 2 - children, in particular younger children will post more of what's on their minds on a social site such as instagram then they will share with their parents (usually). Have your wife (or you, or even better an older, trusted sibling) get an account and follow her so you can see what's on their minds.
Pro tip 3 - until of course, they get pissed off, create another account, don't tell you about it and then really start posting some stupid crap
Not that I'd know from experience or anything.......