Xamarin forms C# Database and payment -- 2

Hello all, I'm developing cross-platform "Android/iOS" mobile application using Xamarin and pure c#, I require the following features. *Feature 1* 1- one registartion button using email/name and phone number 2- Any backend database can be used "Firebase is prefered" but both android and iOS should use only one database 3- The database should store 7 Database entrys for each user 4- The following checks should be done on the 7 Database entrys Note: "Means all the 7 entrys should be saved to the database" entry 1 -> Name should be unique entry 2 -> Email should be valid email "contain @ and .com" entry 3 -> Password should be atleast 8 char long any charachters or number or special signs entry 4 -> Should be intger and between 1-1000 integer means 1,2,3,4.......1000. entry 5 -> should be dynamic length 1D integer array. its length equals to entry 4. example entry 4 equals to 456 then entry 5 should be integer array[456] entry 6 -> should contain string with fixed length of 4 charachters which means only 4 charachters are allowed. entry 7 -> Is Boolean True/False all the 7 entrys should be gathered as folowing entry 1 -> Text Box entry 2 -> Text Box entry 3 -> Password Text Box entry 4 -> Text Box that allowes integer numbers only entry 5 -> A totally new form that has Text box and one button and counter that allows the user to enter the number and click the button untill he fills the whole array. entry 6 -> Text Box entry 7 -> Check Box *Feature 2* 1- Payment through Google pay and Apple pay 2- payment should be done by button. 3- All the payment data are as following UPI ("pa", "email is from entry 2") ("pn", "Name is from entry 2") ("pn", "Data in entry 6") ("mc", "0000") ("tr", TransactionID is random generated number) ("tn", "InAppbuy") ("am", "Amount from text box") ("cu", "Currency is fixed USD") .Build()) *Forms* There are 7 Xamarin basic forms Form 1-> Login "Email or phone and password" Form 2-> Register "Name/Emal/Phone/Password" Form 3-> Forget Password form "Reset password by email or phone" Form 4-> To fill entrys 4,6,7 and continue button Form 5-> To fill entry 5 by one text box and one button and one view box to view the current counter "Array index" Next button Next button is used to increment the array index and the user is allowed to continue filling untill it reach the max then the button name changes to continue once continue is clicked it goes to form 6 Form 6-> to view all the 7 entrys and continue button to go to form 7 form 7-> has one text box and button to buy