you have to click the button in the right and wait to open
Hold down the screen and release to shoot.
You need a 64 bit Android to play and the web version was only an early version that didn't used Live2D now is not possible due performance issues to offer an online version.
You have to complete updated Rangiku's quest first.
iPhone doesn't allow nsfw apps, only Mac when it comes to Apple
PC version contains Windows and Linux