Question About Secure Payment Form Integration

[securemerchant]

Hi everyone,

I'm working on a business website and currently reviewing different ways to integrate a secure payment processing workflow.

For example, I'm looking at Secure Merchant Solution for a payment-processing website and I'm interested in understanding the best practices for integrating a payment form with a modern website.
Visit here- https://securemerchantsolution.com/

A few things I'm trying to understand:

What is the recommended way to validate payment form inputs?
How should payment errors be handled on the frontend?
What security checks should be performed before submitting a transaction?
Is it better to use a hosted checkout page or an API-based integration?
Are there any common integration issues developers should watch for?

I'd appreciate any advice or examples from developers who have worked with online payment integrations.