Sharepoint 2013 online on iPhone app & custom list item form

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iPhone

SharePoint2013

Hello,

I'm using the iPhone app for SharePoint 2013 online, for the default NewForm.aspx for new item this looks really good. But when I add lookup fields, the app shows them as Read Only.
And if I add some dropdown list with jquery, this is not shown in the form (in the mobile app).
So, is this version very limited for list item forms? or this needs to set some settings...

What I have tried:

I have tried to create a new page and add the fields with jquery and JSOM functionality but this option will show the whole master page and this is like open the site in the browser.

So, I need to customize the new form of the listitem adding lookup fields that load data from other list to make selections.

Please can you help to point me to the direction to find out more info.
Thanks,
Jio