What is the oldest Bitcoin Core Client that can in theory sync to the chain tip? I've seen this question regarding the original Satoshi Client being able to sync to the chain tip. The main issues why it doesn't work were:


Change in protocol messages
IRC Node discovery is now disabled
Number of BDB locks too low


When have these issues been resolved? What is the oldest bitcoin core client that can sync to the chain tip (disregarding any problems with the client itself being very slow).
The oldest version that can sync is 0.8.6. This is the version that first used LevelDB instead of BDB. Both the IRC node discovery and the protocol message changes occurred several versions prior.