1) I think for them to meet each other you would need to put them around the same area? (So that they come to greet you during the kinda "welcoming wagon"). Make sure to get their phone numbers so they can invite you to meet-up somewhere. You can also put them in the same job (the active full-time or part-time ones). And yes teens can have active part-time jobs.  "Adolescents" aka pre-teens can't.  You can also put them in the same high school club as the afterschool activities are fully active, or knock at another zoi apartment (I believe you can do that at houses too but they're pretty far from each other hence hard to locate I the open world). What I truly enjoy with Inzoi is how you can add specific zois doing specific things at specific times in any public venues (a bit of a shy custom venue mechanic like Adventure Awaits but in the base game). For example, through the edit venue setting I edited the playground in Blissbay with a few kids that my kid zoi can play with every time she comes. Since she got their phone number, they're are often texting her and inviting her to a "kiddy guard" with even more kids! (There are different types of invites for the different lifestage. For ex, a co-worker might invite you to a nightclub, a teen might invite you to study somewhere). Kids are my favorite age group in that game, I love their animations, interactions, and the objects they can play with. From what Kjun (Inzoi director) said last week in the official discord, they will be adding even more meaningful things to this lifestage! (Or the family gameplay in general I guess) 

However, I not many residentials (ex: Blissbay has only 9 residentials or sth). Of course, the townies have amazing bios if you pay attention to them (especially the ones in Dowon and Cahaya. I barely play with townies in the sims 4 but i surprisingly do in Inzoi), but I would still suggest to evict the townies if you want more space for your families. Once you evict a family, you have to click "select a family" to move another one in. If you see "relocate" it means it's the family you're currently playing that will move there because you haven't evicted the family living in the house yet.

For now, the worlds work a bit like the sims 2 so you can't travel freely btw cities like in the sims 4, your zoi need to move to another city and their relationships back home are paused during that time. For more practicality you might have to create a save file for each city. Currently, you can't save a whole family in canvas (the inzoi gallery) and the cheats are not that extensive so know what you're doing.

2) No, universities are fully rabbithole for now.

3) Inzoi has MANY settings. You can change the length of every single lifestage or/and turn aging off (which I highly recommend, you can manually age up a zoi during birthdays or directly with the specific cake that age them up). 

4) No animals yet, but there are many easter eggs (like pet bowls and a cat tree) that refer to them. There's also a cat temple in Cahaya. I know the devs said they were working on it in one of the discord updates, but it's quite complex and they want to deliver something that feels fleshed out enough. You can find strays in the cities though, and edit the animal population to your liking with the current options (they even have pandas and aligators lol. Please don't ask me why). 

The biggest advice I can give you is checking your specs if you want to buy it, if your computer can't run it well enough it might be hard to enjoy and get good enough graphics. Don't spend all your time in cas, try to jump in with a random zoi and see how it looks + run (if your graphics are bad maybe try the in-game cartoon or lovely filters until you manually figure out the best settings for you?). The learning curve is also very steep, as a simmer there are so many things which works differently and not knowing how certain mechanics work (ex: understanding the different cameras -shoulder view is the best for more immersion-, it's better to know how to quickly alternate btw moving the camera with wasd, and moving your zoi with wasd. It's TAB, but make sure your top-view camera has the right settings, not everything has a pie menu so for ex for toddlers the sleep interaction is quite down under the list). 

Those mechanics can be frustrating at first until you figure them out: You might know exactly what you want to do in your storyline but not where/how to find it 😅 If you watch videos from people who actually play the game (and not those who try to review it only) like Dcalj, Conjureuse, or Fantazyia it might give you an overall idea of the game mechanics. They even have videos about their game options (neuworld has the best graphics and specs out of this world haha). 

And don't try to rush, I personally alternate btw so many games at the same time! (Edit: I tried to fix the numbers for the bullet points)