Iphone 6 features how to use the calendar?

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Why does iPhone automatically delete calendar events from months ago? And how do I make it stop? I use my iPhone calendar a lot and sometimes I rely on it by scrolling to previous months to see when I went for certain appts but it automatically deletes last events without asking? I know I can make special events like bdays repeat weekly or yearly but some events don't require that function, I just want to know when I went to my appts for example, what day and time it was my dentist appt. Can anyone help?
What features does the iPhone 5 has that the iPhone 4 dosent? I know about Siri but other features. And if you could please explain each feature. I'm making sure its worth the upgrade. Please do not convince me to get another brand.
Syncing iPhone/Mac calendar? I've already synced the calendar on my mac with my iphone but I was wondering if it already did or if there's any way to where if I were to add something to my calendar on my phone it would sync and automatically add that event to my mac?
Safari and calendar won't open on my iPhone 4? So i try to open my safari and it'll try to open but eventually end up crashing as well as my calendar. I've tried resetting my settings and hasn't helped at all.