week 4 2/4

I took 40-2 test. It was Abbreviations part. 1 Julius Caesar was born in 100 BC. 
2 Julius Caesar was born in BC 100. and 1 The first discovery of America was definitely not in 1492 AD. 2 The first discovery of America was definitely not in AD 1492.
I looked "The abbreviation AD precedes the date," and "The abbreviation BC should follow the date." I saw may time this pattern, but it is not familiar with me. Just AD( Anno Domini )is before, so its position is located before date?, also BC(Before Christ) follow date? It is just regulation?

The word page should be spelled out. It also I didn't know it. I think that it is just form of writing, but I'm not sure.