Land allotment and refund issue on govt project

Allotment issue: I have applied for residential land in chhatisgarh govt project launched by Raipur Development Authority (RDA) in March 1014 and they have allotted me the piece of land by lottery in Sector-1 on Sep-2014. i was applied for home loan from SBI regarding that and paying EMI for that from Oct-2014 onward. As per the rule RDA is supposed to do registration within 2 year after the development of land, therefore i asked for registration of land on after 2 year but RDA informed me that they cant do registration due to conflict in land and requested to choose some other land in other sector, I choose the land on sector-10 and after 3-4 month after section of new loan after adjusting previous loan SBI given a fresh loan to me for new land in March 2017. Recently i received a notice that the new land in sector-10 is also allotted to some one else therefore RDA cant do registration for that on my name and asking me choose some other land. Now the situation is there is not good land available to choose nor i want to go through the process of reapplying for loan from bank and i want money back with interest. I talked regarding this with RDA and they are saying they can return only the actual amount of land but not the interest part if i want my money back with interest than i have to go by legal process. So can you please suggest me that what i have to do in this case and how much time this will take.