How can I specify a security rule for firestore based on device Platform?

I have a database in firestore which is connected to a Android App, iOS App and a Website. Now for all these we need to sign in to access data.

My question is How can we specify a rule

1. for Android and iOS app, so that users should sign in to access data.

2. And another rule for Website, so that users who access website can decide whether to sign in or not but they can still access data.

Can anyone help me out?