Auto add Subform rows in Zoho Form with custom function

I had created a Zoho Form with Subform to allow user to add in the attendance name list via email link.

I wish to use custom function to auto add row in subform, so that they can fill up accordingly.

Example : When there are 5 person will be attend the meeting, then auto send the Zoho Form with pre-fill 5 row added in subform (Dynamic). Possible to achieve that? If not, what's the workaround method?

2) With the same zoho form, when user submit the name list with subform (Integrated CRM with Deals Subform - Update Record). The record will auto upsert into Deals Subform Name list but not overwrite the data. Possible to achieve this?

3) When the Zoho Form API document will be release?

Thank you

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