How can start SYNC Realm whithout Sync


I know that exist Session.Start() and Session.Stop but whenever create a Realm Instance opening realm db, they start synching, i want open without it.

Other doubt is about flexible-sync, if they automatic manage db store, expanding and compacting dynamic ?

If not compacting dynamic how can i detect unused space and how ideal formula to calculate it to made a batch compacting using Realm.Compact when close db ?