Service tax input credit under reverse charge mechanism

yes you can take service tax credit because it comes under input service defination.

Please pay the reverse charge service tax in a separate challan and use the same as input document to be adjusted (set off) for your other output services.  The service tax accounting/payment code is only one for all the services.  Unde remarks column you can indicate the name of the services forfuture reference.

If Service Tax Payment under Reverse Charge Mach. is paid in same month on last day of month then can it will be available for set off in next month. Eg: I paid service tax on 30.09.2012 of september month laib. then can I use setoff  on 07.10.2012 as Input.

yes you can use it 7.10.12