Is here any full stack developer

Is here any full stack developer like mern stack.

FreeCodeCamp teaches the MERN stack, it’s highly probable you will meet MERN stack developers on the forum

Yes, but not any particular stack.

Doesn’t really work that way in practice – there is some stuff written in {some languages} and some front-end stuff written in {JavaScript | Typescript} using {some framework} and lots of tooling in {various languages} and {some databases} and {some cloud services} and {some CI services} etc etc. You just work with what you have in front of you + a pile of documentation.

What FCC teaches gives you a good idea of the various moving parts involved. IRL it’s very unusual that someone picks some named set of technologies front-to-back, these things agglomerate over the course of time and via the work of many developers.

Yes. There are several of us on the forum who are full stack developers.