Question 1) I use ‘md’ theme (using “theme: ‘md’,”) for both iOS and Android, is that okay, healthy, and natural???
Question 2) I like iOS page transition style (which brings page from right direction to the view), I like to apply that to md theme and use it in place of md’s style, but how???
For Android and iOS design there are specifications for design, animation, etc. You can use your animation, this is not prohibited, but it is recommended to follow the specifications, especially when you have little experience in creating ux / ui mobile app design
It means you should think again why do you use framework.That will bring you lots codes working.You can try to use md icon search in ios theme,you will see.