Is it possible to set multiple alerts for a (subscribed calendar) only? For example, I would only like one of my subscribed calendars to alert me two hours ahead of time. For all other calendars, it can be 15 minutes like default. Is this possible?
I think that if you did this through a Google account you can get it to work. Put the Google account on your device (if you don't have one already) and check calendars (only) to sync (if you're just adding the account to get this functionality). Go to the Google Calendar web page, subscribe to the calendars (by URL), and set the notifications per subscribed calendar. Google subscribed calendars don't appear by default in the stock iOS Calendar app so you have to (in your device's Safari) go to https://calendar.google.com/calendar/syncselect and choose the subscribed calendars that you want to show in the iOS Calendar app.
Not sure what happens when you have default alerts set up in iOS Calendar. You might get alerts at the default times as well as the per calendar notifications that you set up at Google.
Also, Google subscribed calendars don't update frequently (every several hours, I think) so if it's a very dynamic calendar with frequent changes daily then you could run into issues.