Step 1. I back up the wallet and I disconnect.
Step 2. Someone sends me a bitcoin to this wallet and I can see it (in balance).
When you are off the Internet, the wallet software will not know that the transaction occurred until it is synchronized with other nodes in the network (P2P protocol). However, while the sender is online, the transaction will continue to be sent to mempool and will eventually exist on the network (once included in a block) and may spend the output (provided the transaction has been created). correctly).
Step 3. I will restore my bitcoin central wallet to the starting point …
If you have backed up your wallet file, you are basically saving your private keys, which is the only piece that allows you to spend TX exits. If you reset your node or import your wallet into a computer that is not yet fully synchronized, the balance will remain at 0 until the block containing your transaction.
I guess I'll start again 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 have to synchronize 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 it is updated with the header.
If this is correct.