Embedded Site + CSS working on Desktop + Android // Not Working On iPhone

Our shop is trying to embed our Dutchie online ordering page into our SquareSpace "Menu" page.
Utilizing some code solution online + some width/height adjustments, the embed looks and functions flawlessly on Desktop (Win 10) & Android mobile devices. 
iPhones are missing buttons, images & button functionality that works as intended on non iPhone devices. Its particularly weird that the embed sizes proper on iPhones but the material inside the embed doesn't look or function proper.
Any help would be appreciated, Thanks

Notes :

1. On iPhones, specifically the pre weight options are missing from selection
2. Oddly, the embedded "back" button causes actual ios browser to go "back" one page instead of just inside the embed and going back 1 page on the Dutchie site itself.