Stream HR, accelerometer and blood oxygen data from Watch every 30s?

For the development of a sleep app, we want to constantly monitor a user’s heart rate (HR), accelerometer and blood oxygen data and based on that define in which sleep stage a user is. Reaching certain sleep stages should then trigger certain actions on the iPhone, e.g. playing music.

1. Is it possible to stream HR, accelerometer and blood oxygen data directly from the watch? I read older articles mentioning that it is only possible via AppleHealthKit?

2. Can we define how often the watch should measure the data (i.e. every 10 or 30 seconds)?

From what I understand, AppleWatch only measures the HR constantly when users are doing workouts, but not when resting/sleeping. Thus, we would need to adjust the frequency, probably to every 30 seconds.

Thanks for any advice!