First off, welcome to TamaTalk! By the way, your English is just fine for it being your second language.
Anyway, bear with me, I tend to write a lot.
Onto the versions...this might take a while.
I think there are actually 9 Connection versions (counting the V4.5 and the V5.5, which are essentially the re-vamped versions of their respective previous versions, but I digress). I'm guessing you don't know about the Tamagotchis that came out in the late '90s, before the first Connection came out in 2004? Let me tell you, it's a lot to take in but just keep doing your researching and asking questions and you'll get the gist of it eventually. Anyway, the ones that came out before the Connections are what we call the vintage/old-school/ancestor Tamagotchis. The main thing is that they don't have the infrared connection capabilities that the more modern ones have. To keep it short, I'd like to direct you to
THIS page, which lists all the versions of Tamagotchi ever released, even the accessories and stuff. Additionally, if you'd like to learn more about the vintage Tamagotchis, I do have a few sites that I recommend:
THIS,
THIS, and
THIS.
The reason why I mention the ancestor Tamagotchis is because of your first question. Personally, I would recommend any one of the ancestor Tamagotchis if you can get them, especially the Angelgotchi/Tamagotchi Angel. I don't know if you can tell by my user name, but I generally prefer the vintage ones over the Connection ones, though there are many cool things about the Connection versions. If you'd like the family one, that one coincides with the V5 series. Yes, if you were to buy the Tamagotchi in-package, it would say which version it is on it. Which brings me to a different, but related, point.
As far as finding Tamagotchis in stores, you won't be able to find them in stores at all (maybe barring the most recent version, the Tama-Go, but more on that later). Your best bet would be to find them online. As I mentioned above, you will be able to see which version you're getting, provided that it comes in package. A lot of them don't though because of the way it was packaged and used. If this is the case, you'd need to learn how to recognize which version is which by looking at the shell shape, design, whether or not it has an antenna, what type of antenna, things like this. Here's a quick and general run-down on how to distinguish between the different Connections:
The V1 and V2 have a similar shell shape with no antenna. It's a bit difficult to tell between the two if you're just looking at them online, out of package, but V1s usually have simpler shell designs than the V2. Once you get it, you can really tell what the difference is by looking at what type of games they have: a V1 only has 2 games and a V2 has up to 4 games (which you unlock as your character evolves).
The V3 has a little antenna that points straight up.
The V4 has an antenna with a ball on the end of it
The V4.5 has an antenna with a star on the end of it.
The V5 series all have a roof-looking antenna, since it's supposed to be a family-themed Tamagotchi.
The V6 does not have an antenna and would be confused with a V1 or V2 if it weren't for its music-themed shell designs (since the Tamagotchi is also known as the Music Star).
The Tama-Go...well, it's easy to not get it confused with all the others because it's much larger than the others and they come with figurines and designed face plates.
As for your second question, what character you get depends on which version you have, and there are many different characters for each growth phase (there are typically 4 phases: baby, toddler, teen, and adult). Have a look at
THIS forum (TamaTalk Reference) under "The Library" and you'll find all the growth charts you're looking for.
Well! I hope I didn't scare you away by writing a whole ton. It's a silly habit of mine, having to go back and explain all the background stuff before actually answering the questions. It feels more complete that way.
Anyway, I hope this helps and feel free to ask more questions if you have any! Welcome again and I hope you enjoy your time here!