Which daemon is a lightning node running? To run a lightning node we can use 3 different daemons : 
 - c-lightning 
 - eclair 
 - LND

Is there a way to understand which daemon is a specific peer running?
By the lightning network protocol there is no direct means to detect which implementation is used by another node. 

However you could use indirect hints for example the standard cltv deltas or channel fees are different for the various implementations. That being said I could obviously run clightning with the default config of lnd. 

Even if there was a way (like the user-agent header of http) nodes could easily spoof such a header. 

On a side note: just to be clear there is currently a forth implementation that is said to be mainnet ready called Ptarmigan. Also electrum is short of being ready for mainnet.