Am I eligible to teach on classical guitar

You don't need merit or distinction to teach Classical Guitar or any skill that you have developed some degree of proficiency in. I am not aware of any rules which would preclude you from teaching classical guitar as a private teacher.

You might not be able to get a salaried position at a music school or college, but you could hold yourself out as a private "Classical Guitar Teacher" (or Tutor or Instructor). If you have skills that are valuable and have enough understanding of technique and methods so that you don't set up students with bad habits - you might be able to teach those skills to others.

I say "might" because it's not enough to know how to do what you want to teach someone else to do. You must be able to communicate the proper techniques and methods in a manner that effectively facilitates assimilation of the information by the student. Not all great baseball players make good coaches and some of the best coaches in baseball were not the best players.

If you think you have the patience, and the ability to convey what you know to a beginner in a manner that they can digest and understand and execute, then try taking on a few beginning students and see if you can teach them something they find useful and valuable.

You might want to carefully consider and plan your approach to teaching and develop a philosophy that you and your students can embrace. Take into consideration what were the important building blocks that you had to master before moving on to more advanced techniques. Learning to play classical guitar requires learning some basic skills starting with things such as how to hold the guitar and where to place your picking and fretting hands. Of course the student must at some point be able to develop and demonstrate an ability to execute some simple basic finger picking patters.

You might invent a creative new method of teaching the basics that the new student must master, that might be more effective or more fun than the way you were taught.

If you want to give it a try, you might consider offering free lessons to some of your friends (or their friends) that are interested in learning. This will allow you to get a feel for how you like teaching, and how effectively you are able to get your message through and keep your students motivated to put in the necessary time and effort. If your students are successfully learning skills and making progress and you are able to get them excited about learning to play - you can eventually start asking them to pay what they can afford. And of course, once you discover that your talent for teaching is equal to (or superior to) your talent for playing classical guitar, you can get develop a syllabus or course outline and start soliciting paying students.

You might not be as knowledgeable or have the skills of some of the high level musicians who are out there - but if you can effectively convey the material from concept to mastery, while keeping the student engaged and help them develop a passion for learning to play better, then you will be a great teacher!

As Nike says - "just do it!"