MAnaging netcash debit order payment dates

Good Day we have implemented debit orders via netcash and some issues have arose,we have 2 debit order dates.
1) customers that are billed on the 1st choose the 15th in the e-mandate process and when they are billed on the 1st they complain that they chose the 15th , can you make it so that if a customer chooses a debit order date it must change the billing date.

2)Customers add debit order details and then remove it ,but the payment method stays as debit order. can we not make it so that if debit order is chosen there must be at least a primary debit order details loaded which cannot be removed unless a new primary is selected.

3) when the debit orders are submitted some may fail eg insufficient funds can they automatically be sent a link with the invoice url to make payment.

4) can we use the debicheck instead of e-mandate?

Regards