I put the container in a gallon size zip lock bag and then tap the container on the counter to get the flies to the bottom.  Then open the lid and let a few out, hurry and tap the container again to knock them down again and then close the lid.  Then close the zip lock, place it in the fridge for 5m and that slows them down long enough to get them out and into the creature enclosure.  

One is smaller and one is bigger. It should say under description when you purchase. The smaller ones will reproduce more in the tube. After u pour out all them, keep the tube for a while. More will hatch and will continue to hatch and produce more over a few weeks time

The flies come in a container partially filled with a medium for them to lay eggs in/on and a paste that is their food.  Instructions comes with. 

Yes, but the mantis’ would eat them faster than the flies  could reproduce if you are keeping the mantis babies captive for any amount of time after hatching, like more than a day,  there are usually 100’s of baby mantis’ in one egg sack.

Pretty sure air will go through tubes or else they would have died in shipping.

As with all flies until they grow up they will jump around to get where they want to go, including if you take the lid off with them near the top; they will hop out, so it is best to knock them to the bottom before opening the lid and tap them into another container of the amount needed. An empty container gives them little to grab onto so they will stay at the bottom while you transfer it to the hungry resident whose lunch they will be. If left in the culture too long they will run out of food and die, so use them, don't save them.