The main type 4 law right now is the one California passed and some others copied.

It requires that the parent be able to enter an age or birthdate. The API that the OS must provide to apps is required to let apps ask for age ranges, with these ranges required: [0, 13), [13, 16), [16, 18), [18, ∞).

The California bill is mostly fine, and just needs some tweaks. It is way narrower than 99% of the people who comment on it think it is.

From what little that has actually been disclosed about the federal bill it sounds like it too is taking a parental control approach, but it also sounds like it might be requiring the OS to actually verify the age.

The big question is what does that mean? If it just means the OS has to ask the parents for the age it may be similar to the California law and might just take some tweaking. If it means the OS has to be provided actual proof then it is quite different and much more problematic.