Subscription Question from Website to iPad

1. If I create a website and have users login and purchase a pricing plan from the site, then when they login to my App on the iPad, they can have access to all the features on the iPad. In this case, am I still required to give Apple a 30% cut?

A. What if the website doesn't have any features but just a landing page with login/signup and an option to purchase a pricing plan. Once user purchases the plan, they can then go to iPad and login and they'll have access to all the features based off their pricing plan. Would I still be required to give Apple a 30% cut?

2. What if I don't create a web app and all I have is an iPad app. If users can signup/login in the iPad app and if they want to upgrade to premium, they can purchase a subscription. Can I have a popup box asking them to purchase the subscription service on our website with a clickable link to my website inside the iPad app? What if I i don't have a clickable link to the website though so users won't be able to go from my iPad app to the web app and I just inform them and give them URL of website in the popup box in the app and it's not a clickable link. Is that allowed?. Would I still be required to give Apple a 30% cut?