#1- What is the exact Sharp IR rangefinder's model number AND range ?
As far as im aware it doesn't matter, just choose a range that suits you, around 10cm-50cm
#2-is the 5v linear regularor positive OR negative ?
#3- Is the 220uF - 16V capacitor ok? (parts list doesn't mention V value)
The voltage doesn't matter, normal rule of thumb is higher rated voltage the better (but keep it realistic for you project)
like don't use a 450V cap in a 5V circuit like me lol (that's all they had left in stock).
#4- 340 ohm and 1,62 ohm resistor ok at 1/4V ?
I think you mean 1/4watt which should be completely fine
#5- What LED to select (3mm or 5mm )?
as already said this is just the casing diameter, only worry about it if your fitting it into a housing.
I know most of these were already answered but I'm just offering my opinion