Can saved credit card data be accessed in Pay Now invoice links without login?

[Ram_A]

Hi there! 
Would appreciate any help with these questions.

Regarding our current payment setup, particularly concerning third-party payment gateways and the functionality of the Pay Now email invoice links.

- Suppose I enable checkout without login.
- Suppose I I only use a 3rd party payment gateway. "shopify payment not support my country".

1. If a customer, who previously made a normal purchase using our website while he logged in and chooses to pay online using third-party payment gateways, and their credit card data is saved for any future purchases. Then in his next purchase he decides to manually pay through an invoice link , will the payment page display their saved credit card information while he is not logged in, or will he need to enter the card data again? 

2. When we send a"Pay Now" email invoice to the customer, enabling them to use the "Pay Now" button, it will direct them to the payment page without requiring a login. Will the opened payment page support the third-party payment gateway we already used, or is the "Pay Now" link exclusive to Shopify payment gateways?

3. If I made the logging in to make a check out is mandatory, does this help with question1 or 2?

Thanks