Long and short, you cannot completely. You can continue to use the APIs that are available in 3.1 for an extended period of time. However, if 4.3 devalues ββany method that becomes deprecated in 4.4, and you ignore the obsolescence warning, you will have problems.
- , 4.2, , . respondsToSelector: , . , , , 4.3, Apple, , API, , , , , .
, , , 100%. , , ( iOS, ).