Get Streams for things like viewers, and to calculate how long they’re streaming https://dev.twitch.tv/docs/api/reference#get-streams
Get User Follows for their total followers https://dev.twitch.tv/docs/api/reference#get-users-follows
Twitch does not provide you with any historic information, if you want to know averages, hours watched, viewers etc… then you need to poll the endpoints are regular intervals and track all that data, ideally with permission from the channel involved, and perform any aggregation/calculation yourself.