I have to agree with Mary Catherine.

Don't get on the plane and come here unless you are 100% convinced that HR will allow you to leave for your holiday.

The person recruiting you may well be just telling you a pack of lies to get you on the plane, knowing that once you are here, you can't leave without the express permission of your sponsor, and s/he doesn't give a damn about whether or not you attend a Christening.

Your sponsor may well say that your RP process won't be complete by the time of your intended leave, so if you exit the country at such an early stage the whole RP process will need to start again from scratch. Or you could be told that you can't take any leave during your probation period, or they may say that you haven't worked long enough to have accrued any leave days.

Basically in answer to your question - you can NEVER leave the country unless someone has approved your exit. And wanting to exit so soon after arriving won't be seen in a positive light by many employers.