Damage deductions / improvements on rental property

Long story short.  We converted our home to a rental property in August 2016.  We owned and lived in the home since 2012.

From what I understand an improvement expense can be entered regardless of when it was done.  IE my central AC system was installed in 2014, but I still put the expense in because it brings up the depreciation value?  Do I understand that correctly?

Next is repairs.  Obviously we've had repairs over the years since living in the house.   Does this fall into the same circumstances?  I have the receipts from all repairs done since we bought the house.  But do I need to put those all in or is it only repairs since the unit became a rental.  And further on that question, what about repairs made to make it ready for rental (the couple months prior to switching it to a rental property)?