Hi! I am Maksim from Ukraine (UTC +2)
This is the great approach to ask questions.
A. We use frameworks Symfony, Laravel, Yii.
B. We have worked on the system for tracking conversion of targeted advertising. Facebook API.
C. We developed marketplaces on Shopify. I will be honest with you not a lot but we have experience.
D. Yes. with WordPress and Woocommerce we have huge experience since it is a really popular thing on a market.
Few words about us we mainly work with PHP. We have strong Full Stack team and will be happy to help you with your approach.
We look forward to hearing from you soon!
Kind regards