a credit card / credit card(s)

[Itasan]

Do these all work?
1-1. Do you accept credit card?
1-2. Do you accept a credit card?
1-3. Do you accept credit cards?
2-1. I'll pay by credit card.
2-2. I'll pay by a credit card.
Thank you.

[Lorikeet]

Do these all work?
1-1. Do you accept credit card?
1-2. Do you accept a credit card?
1-3. Do you accept credit cards?
2-1. I'll pay by credit card.
2-2. I'll pay by a credit card.
Thank you.

1-3 and 2-1 are the ones I'd accept.

1-1 is just plain wrong
1-2 would be okay if it was "Would you accept a credit card?" (I think "Do you is more general and needs the plural.)
2-2 sounds wrong as well.

[Itasan]

Thank you very much, Lorikeet. All the answers are very
instructive as always, particularly the following information:
1-2 would be okay if it was "Would you accept a credit card?" (I think "Do you is more general and needs the plural.)
Thank you again.