Granting of leave for xx number of days is the prerogative of the company management. They may or may not approve. They can even say only these many days can be availed and want the employee to report back on so and so date due to urgency of work etc.
Coming to calculations SL cannot be taken for a marriage. If the company policy allows to club CL and PL you may try to do that. When does the PL comes into effect? After completion of one full year in the company or after probation? Most of your questions ought to be available in the company policy itself else see that it is included at the earliest.
After checking the PL you may add what is available as on the leave applicable date and rest put it under LoP, provided management is okay with allowing full leave of 15 days.
Thanks and Regards
14th February 2019 From India, Hyderabad