There are many rules relating to regularisation.
There are many clauses that run counter to the general rule that a worker working for more than 240 days a year is to be absorbed.
The government has been one of the biggest violator of labour laws.
And they have a battery of lawyers to fight their cases for years together.
So, while under the law you can file a case, the reality is that you need huge amount of money, or a benefactor to support you. You will read in the news papers of agitation, strikes etc for such cases. You will then realise that this is common, and people have had to take to the streets to fight. Alone, you are unlikely to achieve anything before your money funds out (what is the possibility your job will be retained after you file a case ?)