Numbering appendix like headings

I need this:

1 Chapter one (Ctrl+1)

1.1 Chapter (Ctrl+2)

2 Chapter two (Ctrl+1)

A Appendix one (heading 1 like)

A.1 Chapter (Ctrl+2)

B Appendix two (heading 1 like)

I can manage to reset the numbering at “A Appendix one”, but when I set it to use letters instead of numbers, then all Headings 1 are also set to letters: chapter one → A, chapter two → B, appendix one → C

How can I restart the numbering and the style of numbering of headings?

Such a way that subheadings can be used and follows the new numbering scheme (A.1, A.1.1, B.1, B.2., etc…)

See this question and this one.

The second one contains screen shots explaining the procedure extensively.