Thank you very much for all replies.

I have learned many things. Used a lot of google to understand most of the abbreviations. But the thing that shocked me is the definition of Mexico as a North American country, which in this case turns out fine for me.

As suggested, main destinations aimed in this trip are S. America and South Pacific, and possibly a couple of Central American countries with an open jaw between Mexico and Bogotá/Caracas. Does the OneWorld Circle Pacific fare allow for international open jaw or only for domestics?

If you allow me, a couple of fine-tunning questions:

1) Is a possible flight between Santiago - Mount Pleasant - Santiago - considered a case of backtracking or is permissible under fare rules?

2) Let's say in next 5-6 months is it to be expected that Star Alliance will rival OneWorld Circle Pacific fare by including Continental Micronesia flights into Star Alliance Circle Pacific fare or OneWorld will remain the best option to combine S.America and the Pacific?