What law? I've used this account since gmail started, now they need to know more personal details? Seems if I don't enter it I will be locked out of my phone and all google services.
#2: Do note, they want 'a' birthday. Why would you ever consider giving them a real anything? Online services that 'demand' unnecessary metadata, where you decide to give metadata to continue to use them as opposed to dropping them, *always* get fake metadata.
Years ago the washington post used to demand some unnecessary metadata to read articles. I was a 98 year old from Mongolia one day, a 65 year old Peruvian for the next, and the answers were different, and fake, every time (I'd clear their cookie immediately to trigger another 'ask' for the next time I would click on a link to them).
As an addendum to the above, make sure you remember or record what birthdate that you give them in case it's needed for verification or account recovery at some future date.
I can think of the most known Children’s Online Privacy Protection Act (COPPA) and some EU safeguards that prevent you from processing a child's personal data without the guardian consent.
I would also guess that there are content restrictions that might be hard to implement on a Google account and they prefer locking children out of their platform. I do think Facebook and many others applies the same method.
Disclaimer: This is not legal advice