I'll explain the steps I want to figure out.
I have an empty bitcoin core wallet.
I backup the wallet and go offline.
Someone sends bitcoin to this wallet and I can see it in balance.
I restore my bitcoin core wallet to the initial point.
What will happen then?
I assume that I'll start over with the blockchain from scratch and what will happen is that initially the balance will be 0 (since my node is not yet aware of the transaction). So I'll need to synchronize up to the block where the transaction was included (this will take some time). At that time the balance will be updated. After that the synchronization will continue until its up-to-date with the head.