How can I Schedule SMS for future?

You can schedule any number of sms in future by going to Push SMS -> Compose Schedule SMS . You can schedule either by group or single.

Is there any maximum limit to schedule sms?

No , there is no maximum limit . However for better throughput please schedule only if necessary.

How do I check If the message is scheduled or to delete the scheduled message before delivery?

You can manage your scheduled sms by going to Push SMS - > Manage Scheduled SMS . You can delete by clicking on the delete button to delete the scheduled messages.