Builder charging interest @ 24%; built extra flats

Hi I booked a flat in Mahaluxmi Homz, Ghaziabad in December'14. The payment plan was 10% & 90% on possession. However, I am new buyer & had no clue regarding the way flat is purchased; they never mentioned by when the flat will be ready & what will be the penalty clause. They never even gave any sales deed for that matter. In April, I was asked to pay 90% money since they were giving the possession (so called) in April'15. However there was no road (its near village), no LPG connection, no proper parking, & even flat was not flat but just cemented walls. When I asked them these questions they never replied & told me that I will get the flat ready only after the payment is given...the time they told me was 1 month I started arranging the money; however even if I had given the payment, i would not have shifted because of the road that was not constructed, it was prepared in July itself I arranged the money & gave them all the money as per their demand letters. I was suppose to shift in first week of September, however immediately after the last payment done; I was informed that I need to pay interest of Rs.2.21 lakhs!...Also, my flat got ready only in last week of August! How come they can charge the money without ever mentioning in the receipts, (no receipts ever mentioned this) which is totally a ransom; since I have given the entire amount & after they started asking for the interest amount. 2. They charged 3% service tax; however I personally think even that is not required; pls clarify 3. On the top of that they constructed three extra flats on the club house which was not mentioned earlier in the brochure...infact they got approvals in last 2 months from GDA, which again is cheating Pls advise, should I move to consumer court & how I can put a stay on those flats.