2/ I said we don't use any (mobile) SDKs from 3-parties analytics, but we do use their backend (Segment, Amplitude). We send the requests from our anonymous proxy directly to their servers.
I was worried that mobile SDKs would leak other data (iOS version, device size, ...) that I don't want to know about. And as a general rule we don't like to use SDK/code from 3parties for security reasons.
3/ We use analytics to track how many users are using the app, and how many users are using the cleaning features. This data does help us to make strategic decisions.