Is employment bond legal and enforceable in my case?

I got placed in a company based in New Delhi in june 2016. I was told to sign a bond which says that if I leave company in my training period(1st 12 months) or in 4 years after training completion, I will have to pay company Rs 3,00,000. I was not getting any other job so I signed the bond. After joining the company I realised that it is not a good company. They did not have good projects to work on. They just gave me some documents to read in the name of training. I was made to work on projects from 2nd month of training. Although I did not know what I was doing because I was made to learn everything on my own. Even salary of all the employees was coming late because they did not have good projects. Then after 6 months of working I quit the job without giving any resignation (because If I had given resignation they would not have accepted it and I would be scolded by my Boss as I saw happened with others) and came back to my home to prepare for govt exams. Now I am getting notice from their lawyer that I have to submit bond or they will sue me in court. I want to know Is this kind of bond legal which is completely one sided? Can they really challenge me in court to get the bond amount? Will their claim hold in court? Can I work in any other Pvt. or Govt job without paying that bond?