RE: constraint
Hi Ranjana
All tasks have a constraint set. You can remove a partial or full constraint by setting the task back to the default Start as soon as possible setting.
To do this double click on the task and go to the advanced tab. Set the constraint type to "As soon as possible". Any constraint date already applied to the task will be removed when you click on OK.
I hope this answers your question - do let us know if we can be of further assistance.
Kind regards,
Andrew