Dear friend,
Any leave other than Sick Leave requires prior sanction. No employee can claim leave as a matter of right.
Asking for the sanction of a particular leave is the choice of the employee subject to the position of it's credit in his leave account.
Being absent earlier and asking leave later is indicative of the poor administrative control of the Employer.
If it is the usual and informal practice of your organization, you can do so.
No statutory restriction on the minimum number of any kind of leave to be claimed.