Android and iOS app - Message Scheduler

need a app on android and iOS for a message scheduling service
this will have 2 versions - free and paid
essence of the app is that registered user can record video / audio messages and then schedule to have them delivered to a recipient via whatsapp / sms on a later date, OR immediately - if delivered immediately, the media file will only be available on the later chosen date

example - if your birthday is on 5th June, i can record a video message through the app today and schedule it to be sent to you on your birthday, OR even today (if i chose today, then you will get a message informing you that i have sent a message, but can only be opened on 5th June)

this needs to be sent via whatsapp or SMS, depending on what the user wants

free version will have limited video / audio recording time
Free version, user cannot edit or delete the message once schedules
free version will be ad supported

paid version will have higher limit for recording time
paid users can edit messages or delete them
no ads

both free and paid users will need to buy pack of number of messages that they can send

we will also have a sales team, who will drive the number if paid users - we will need to generate unique codes for each sales person when they sign up through our website module - sales people will get commission for each paid used

on the user front, they will use the unique code that the sales people will provide them, and get a discount on membership

app design has to be simplistic and clean

please revert with:

1. Estimates cost
2. expetrnal dependencies that you would require (for example, to build user database, sales people details, server space to store the recorded media, API's for sending whatsapp / sms etc
3. estimated time to be taken