Custom Router Firmware

Hi, kindly let us know the following: - what is the coding language for the router firmware - which router firmwares can you build (i.e. which brand/model). We are looking for a software that works with Peplink (or poplin AC one mini) We are looking to build a standard router firmware with the following features: - ability to login to facebook after connecting to WIFI, before users can get internet access - after login to facebook, customer details are captured from facebook - ability to integrate with our existing CRM system OR ability to send emails from this firmware. We will NOT reply to templated responses. Kindly read our requirements properly and reply accordingly. Thank you.