basic question: can I have multiple programs in a project and can I reference resources from program1:devstack to program2:prdstack ?

can I have multiple programs in a project

No, a project contains one program

can I reference resources from program1:devstack to program2:prdstack

yes, using a stack reference: https://www.pulumi.com/learn/building-with-pulumi/stack-references/

thanks for the quick response. I am migrationg from cdktf to Pulumi and figuring out the best way to design. My code is of tens of thousands of lines with 100+ stacks which interact with each other (across 3 cloud providers). I figuring out the design which is agile and scalable using pulumi.

We are happy to help: https://www.pulumi.com/contact/

You may also find some of our recommended practices helpful, check this blog series: https://www.pulumi.com/blog/iac-recommended-practices-code-organization-and-stacks/

that helps a lot.. thanks

Happy to help!