Is there any way that I can get my raspberry pi boards terminal on the browser of another system connected in same network ; if any open source application is available to get remote access through port 80 that will also get the job done . All other Ports are closed , only available port is port 80 . The board is running Debian Version stretch . But I am not considering using Reverse Tunneling .
This does not seem possible, port 80 is the default port for http. Which is probably being used by a process that is serving a web app for the server.
At most you will be able to interact via REST APIs and/or SOAP but neither can give you remote access/control of the device.