Apparently the climb classifications (4,3,2,1,HC) in the Le Tour de France are based on the gear you’d need to use in a 2CV to get up that hill. This is quite clearly horse poop and – as the owner of a 2CV – I have a 100% subjective personal anecdote to prove it:
The Le Tour has been past the village were I grew up twice (’94 & ’07) and both times there was a 4th cat near by. There’s no way you’d get a 2CV up those hills in 4th – they’re solid 3rd and maybe a quick dip to 2nd near the top if you didn’t get a good run at them on the way in.
As for HC (which is supposedly impassable to a 2CV) I similarly call horse. 1st gear in a 2CV is so low it won’t even get you half way across a set of traffic lights without needing to change up – you’ll run out of grip on the tyres long before you torque stall the engine. (Admittedly the grupetto would be faster up the hill but that’s not the point.)
Generally your biggest problem on hills in a 2CV is some idiot in a modern car in front of you that slows down for the corners – it’s all about conservation of momentum, as this person ably demonstrates.