Force any Employee to sign these Legal kind of Documents on last

Hi I am Manish Chhipa working as a Software Developer in IT Company of Jaipur since last 4.5 years. I have resigned from my Current Position on 25th of march 2017 and served 2 month Notice period as its Company policy. After Completing 2 months Notice Period When I went office to Collect my Documents to Management they ask me to Sign a Legal Documents on 500rs. Stamp and told me that If you need your Salary and Documents then You have to sign the Agreement. I was shocked and not aware of this this kind of Legal Activities. When i joined the company neither they informed me about this or nor i have signed any kind of documents with this info. Company Points : 1.I can't contact company old and New Clients . Query : I don't know Who is your Client or Not ? Will you provide me all your Client List to whom you worked and to whom you are working and you will work in Future so that I can avoid these kind of circumstances ? 2.I can't contact company old and New Employees. Query : Will you Provide me all your Employees list Old and New ? In future If any employee want to work with me after completing his/her period or office hrs. then How can i avoid these kind of situations ? 3. I can't show any Projects that i have done in last 4.5 yrs. ? Query : In this case what should i write in my resume or Portfolio ? If i join any company then What should i say him that I can't show my Projects to you as its Illegal ? Except from this I have 2 more Query : 1. Why should i sign these kind of documents ? 2. Is it right/Legal to force any Employee to sign these Legal kind of Documents on last day ? I am getting too much frustrated and mentally harassed that What should i do in this case ? Please Help me. Waiting Positive Response from you. Thanks Manish Chhipa +[deleted]