That's okay, I don't mind helping you understand the cycle a bit more, it's important that we all understand it regardless of what tank size we have
So do you get the part that there are good bacteria (Beneficial bacteria or BB commonly abbreviated) that grow in the tank, mostly in the filter so that's why it's important to have a filter; they like the fast moving waters and the sponges provide lots of good place for them to grow on. These good bacteria help keep our fish safe by turning ammonia (fish poop and other rotting stuff) into nitrite which then are turned into nitrate and taken out of the water with water changes.
The cycle is the same through any tank size, so in your 2.5 all you need is a filter and once your bacteria grow in the filter you can just change water once a week or once every two weeks (for an ADULT fish though, for your baby you will still have to change water daily until he is an adult fish). These good bacteria eat ammonia and so without ammonia, they will starve just like your baby if you don't feed him! So this is why there are a few different methods to feed your bacteria.
First method is the most used method called the Fish-In Cycle, you've probably seen that one before? As well as Fish-Less Cycle? Well in Fish-In, it is as it sounds; you are using your fish as an ammonia source to feed your colony. In the Fish-Less cycle you have no fish in there so your bacteria doesn't have food yet. You have to supply the food by using something ammonia based, often we use 10% ammonia from a hardware store as long as it doesn't have surfactants in it and doesn't bubble when you shake it. So that ammonia is dropped in the tank with a dropper, that is the bacteria's food; kind of like a liquid diet if you want to think of it that way :) Other ammonia sources, you an use a regular shrimp you would find in a grocery store, like ones that people eat. You can get a mesh bag (easy clean up when you want to take the shrimp out) and put it in there, the dead shrimp gives off ammonia for your bacteria to eat.
Does this make sense so far? So basically you want good bacteria, they grow in your filter and keep your fish safe. To grow your colony you need ammonia to feed them. With me so far? I'll explain more if you understand this part :)
And as for the snail crawling out, it depends on the kind of snail. Nerites are escape masters but generally I've found they don't crawl out if there is enough food. Mystery snails will go out of the water but they don't tend to wander far out of the tank. Some snails cannot survive long out of water at all so they never go out. Also, take in account that Nerites are exeptional cleaners, one Nerite can clean an entire 10 gallon out of algae and biofilm in just one day, just think about how much food it will need in your little 2.5 gallon. I suggest you get a small tank or vase and put it on a window sill with smooth rocks on it, this will allow algae to grow on it for food for your snail, you can switch the rocks out weekly or so to feed them and then let the new rocks get algae on them. You want a really nice coating of green algae. I would start this now so you are prepared.