The largest brass inlet is the fuel, the medium size one is the vacuum and the smallest is the oil.
The two black plastic feeds are overflow pipes. These pipes are connected together with a pipe and vented through a cut in the tube.

It can be fitted with the standard manifold, but it wont use the 2 little locating rubbers that's on the top of the manifold.

19mm would be better unless you are planning to go to something more highly tuned in the near future.

It depends what size your standard air box is, if it's 32mm it will fit on. If not you will need to use a open filter with a 32mm fitting. 

Fitting non-standard carbs aren't always a direct bolt on I'm afraid.
The most common things we find is you sometimes you need to check the length of the throttle cable after fitting to match the carb to make sure it is lifting the slide all the way to the top. You also need to have an air filter or air box with a 32mm fitting to suit the TNT carb and the inlet manifold needs to be a 25mm push fitting (Gilera DNA inlet manifold is 25mm as standard)
Then it will be a case of setting the jetting etc up to suit your moped.

the idle jet is 50

No, you will need an adaptor for speedfight because speedfight uses an unusual manifold as standard, you'll need something like Stage6 inlet system or manifold adaptor

Yes it will but it's quite a tight fit, you might need to warm the manifold gently first.