Dms can change any rule they see fit for their party

How would I know if this spell is for Paladin's by only looking in the PHB? It's not shown as available for that class. 

Never mind. I see it's an Oath option. 

im playing a homebrew emo batfolk and he makes use of this all the time due to his fascination with rescuing other batfolk from demonic rituals

magical unconsciousness is apparently a condition that lesser restoration can fix

Quote from yogg_saron >>

so lesser restoration would cure hangovers

If you treat hangovers as being poisoned, then yes it would. If you treat it as something different, then by RAW, no it would not.

I mean, logically it really ought to be able to cure a hangover if it can cure a deadly eldritch disease that causes bleeding from the eyes and eventually blindness, but that's just what RAW states.

A DM can change every rule.  It's a game

I've always ruled that Hangover isn't poison, it's exhaustion from not sleeping.

i think it wold be cool if it cold do any condition.

A dm can basically do as they wish