To meet the technical requirements for VNetwork1, what should you do first?

Creating a new subnet on VNetwork1 is the necessary first step because the technical requirements specify that Azure Firewall must be deployed into a dedicated subnet named AzureFirewallSubnet. This subnet must have this exact name to function correctly. Without this specific subnet, the Azure Firewall deployment will fail. Removing NSGs from existing subnets (Subnet11 and Subnet13) is not a prerequisite for deploying Azure Firewall and could potentially expose resources prematurely. Associating an NSG to Subnet12 might be a later security step but doesn't enable the firewall deployment itself. Configuring DDoS protection for VNetwork1 is a separate security measure and not directly related to the initial deployment of Azure Firewall.