- How to change the text frame on the imageA?

Edit your offline payment gateway within CBSubs > Gateways then adjust "Payment "are you sure?" popup text (blank to disable popup):" as needed.

How to ensure that this option does not appear on the menu (sew imageB)?

You can't remove it without editing the XML file found below.

/components/com_comprofiler/plugin/user/plug_cbpaidsubscriptions/xml/edit.front.invoice.xml

I want to translate this part or make it go away but I have not managed to find it in the code (sew imageC).

Believe that's your gateways name. Edit your gateway within CBSubs > Gateways and give it a more appropriate name.

I would post the password in the custom message plan but the tag [USERNAME] doesn't work. Is there a way to do it?

What message, please be more specific.

For imageB, is that mean that I only need to delete the xml file so that it disappears from form?

No, you need to edit it and delete the XML element for the input you want to remove from the invoice address display.

For imageC, can you tell me what options are used because I just put the name of the module credit card supplied with your module?

You can put whatever string you want. Language strings are supported. That message is supposed to say how the user paid. I've no idea why it says "Not Available" unless that's the name of your gateway or payment method.

Question 4, the message is :
Email on first activation -> Thank-you Email body (subscription active):
or
Email on pending first payment -> Thank-you Email body (payment pending):
In these messages, the tag [USERNAME] does not work

Substitutions are supported in both of these emails. Assuming your username field is enabled and on a published Tab it should substitute in perfectly fine. Try [username] and if that doesn't work check within CB > Field Management that your username field is set to display on profile, is enabled, and is on a tab that is published.

Password will only work in very limited locations. For example the Pending email within CB > Configuration > Registration as at that point in time it has not been encoded yet. You won't be able to send password in any of CBSubs emails as the password will be encoded by then and it can not be reversed.