After choose view import, how to exit this mode?

On iPad there should be icons top left, the furthest one to the left should be the Albums icon. 

They don't seem to be there on your screen grab. Maybe quitting Lightroom and see if it's there when you sign back in?

Tap on one photo and you should be taken to 'Edit' mode.

Tap the tree-dot icon [...] what do you see?

My iphone shows a 'back' icon [<] on the top-left of screen that gives me library view options.

(My iPhone screen)