Flat registration and other pending issues in apartment

Q: Hi,

I booked a flat by paying 50K in Dec 2010 & paid remaining cash 40% (of total amount) in 2 months. Flat completion date was Dec 2011, but got delayed and we got possession in Dec 2012. As per agreement, builder can max delay for 6 months only. Now there are 2 main things for which I need suggestion?

1. Builder is asking for extra service tax as ST got revised after March 2012. If completion is done on time, we cld have get registered it before that BUT we got the registration on July 2012.

Does builders have any legal rights to ask for extra ST? What option I have?

2. Club house and other amenities, got completed recently and Builder is not allowing ppl to access even if u have 1 Rs as pending to pay...People have not paid full amount as pending work is going very slow and still lots of things, like service lift, permanent parking etc are pending....

I want to know mainly abt extra service tax builder asking and what legal option we have to against builder?

Thanks in advance
Anand