Dear @Ronald_Munjoma, I appreciate for your time and energy, devoting to help me. I am very surprised to share what I know that @Friendship_Bench is Zimbabwe's well known mental health study by Prof. Dixon Chibanda (I am fellow by Chibanda et al project).
On to my problem, you rightly converted well what I was thinking finally. PHQ9 is a bit validated here in Ethiopia for respondents to understand well. The first option (not at all) is omitted from the original version and replaced by screening question to be (Yes/No), and main questions (phq1-phq9, follow up questions) will be asked based on previous yes/no response. If the answer is No for primary questions, follow up questions will not be asked. That is why calculation becomes difficult. As an example:
Phq1_screening: Little interest or pleasure in doing things? response: Yes (1), No (0)
Phq1 (part of total score, main question): If yes to previous question, how often did you feel during those two weeks? response: Several days (1), More than half the days (2), Nearly every day (3). So, not at all (0) from original version is omitted here and replaced by screening question Yes (1), No (0).
I have seen SSQ14, and its made ready to be asked for all eligible participants, e.g., male only (right?) and if response is not male, survey ends (?) and seems there is no skip interference for summation as survey it doesn't apply for females?
We will see if others have a solution for the type of mine Yes/No (screening) followed by other questions (skipped if No), and the total score could be generated. coalesce(${var1},0) or default (null to zero) attempted and didn't work.
Further clarity from @Ronald_Munjoma: to be more sure if you could drop more suggestion (I have seen in your form), I am not using "Groups" totally in my ODK form as a response out of one group might affect responses in another group. Does it matter if I don't apply groups?
*I am not clear of using ==> selected(${gender}, '2') OR ${gender} = 2 (in your form)? as I am using the later one, ${gender} = 2, in my form.
What I understand finally is using the original version type of PHQ9 as you recommended for this ODK form as far as it doesn't affect the responses.
Really, thank you @Ronald_Munjoma