How to create a dedicated M365/Azure Sandbox Tenant for product development as a Tier-2 CSP Reseller?

Hello,

Our organization is an enrolled Tier-2 Cloud Solution Provider (CSP) partner (Indirect Reseller). We are currently developing and testing custom products/solutions intended for our end customers.

To safely build, test, and validate these applications without impacting our active production services, we need to spin up a dedicated non-production Microsoft 365 and Azure sandbox tenant.

Could you please clarify the following points?

1. What is the standard process or path for a Tier-2 Indirect Reseller to provision a fully featured M365/Azure developer sandbox? Should this be initiated via the Microsoft 365 Developer Program, or is there a specific path through the Partner Center or partner benefits packages?
2. If the capabilities require our Indirect Provider (Tier 1) to initiate or provision a sandbox reseller relationship environment for us in the Partner Center, what specific permissions or setup do we need to ask them for?
3. Are there specific Azure/M365 partner action pack or benefits package SKUs we should look out for to keep this testing tier cost-effective and non-expiring?

Thank you for your assistance!