About your first question, non-renewing subscriptions can not be restored or sync via the usual Apple way of providing restoring/syncing between devices. You have to provide your own mechanism.
You can check this documentation and judge yourself how you want to do it.
You can sync and restore non-consumables and auto-renewable
subscriptions across devices using StoreKit. When a user purchases an
auto-renewable or non-renewing subscription, your app is responsible
for making it available across all the user's devices, and for
enabling users to restore past purchases.
Regarding your second question:
You can check how your app relates to the following entry in the review guidelines.
"(v) Account Sign-In: If your app doesn’t include significant
account-based features, let people use it without a log-in. Apps may
not require users to enter personal information to function, except
when directly relevant to the core functionality of the app or
required by law. If your core app functionality is not related to a
specific social network (e.g. Facebook, WeChat, Weibo, Twitter, etc.),
you must provide access without a login or via another mechanism.
Pulling basic profile information, sharing to the social network, or
inviting friends to use the app are not considered core app
functionality. The app must also include a mechanism to revoke social
network credentials and disable data access between the app and social
network from within the app. An app may not store credentials or
tokens to social networks off of the device and may only use such
credentials or tokens to directly connect to the social network from
the app itself while the app is in use."