Service tax

Hi Good Afternoon to all

I have query on Service Tax.

1. When can we take cenvat Credit, is there is any transactions limit so that we hv to cross 1,50 lakh, after that only we can claim service tax input credit..?

2. my client is newly registered in service tax, and with in 3 months he crossed 10 lakh, til 10 lakh he has not collected any service tax from customers, now after 10 lakh he's going to collect the service tax from customers and remitting the govt, my query is whether he has to pay ST on previous 10 lakh, ...?

Please help me out friends ...