Can you play against bots as many times as possible or is it just a tutorial thing? Can you level up against bots? How many placement matches are there, and is the match making system good or broken as fuck? How many smurfs are there? How often does someone pick your character? How does kicking other players work, like if I suck too much, can they kick me?
You can play against bots as much as you want, and will level up playing against bots. I'm not sure what the current rules are - it used to be that after Lv20 you would only be 'credited' for a certain quota of bot games per day, but I think they changed that a while ago - but it's certainly a great option for leveling up early on.
Blind Pick Normals and ARAMs are also options. ARAM has a super-fast turnaround, though it's of limited use for learning the nuances of the actual game. You
shouldn't have people acting like dicks to you for being new in ARAM, because it's really just for fun and kind of silly to get upset over losing in one, but... well, online games. There probably will be people raging at you.
Because people believe in Elo Hell - that they're secretly much better than their League/matchmaker rating indicates, but it's just all the plebians holding them down - most people who are in higher leagues are reluctant to smurf. The majority of smurfs are people who believe their main account is in Elo Hell and that they are going to rocket up to their "real" Elo by breaking the chains of that association... in other words, they're mostly pretty crap players that aren't likely to run a clinic on you. You used to see a lot of high-Elo smurfs due to excessively long queue times for 2000+ Elo players, but the League System has made that less of a problem.
You can't be kicked from a team. A player can report you for being an unskilled player after the game ends. As far as I know, reports for unskilled play never result in an actual punitive action unless there's evidence you were intentionally feeding the enemy team or otherwise being unsportsmanlike. I'm actually not sure why the option for them exists; between you and me, I think Riot flags people who make 'Unskilled Player' reports as self-important douchebags and ignores any other reports they send.
You will probably have, on average, two people threaten to report you in any given game you played. They will most likely have no logical reason for doing so, or even express reasons that are not reportable/punishable ("He had first pick and picked a mid, but I called mid first and I'm really loud!", "He picked Teemo, you aren't allowed to pick Teemo!", etc.). Feel free to ignore them, the algorithm for reporting gives their reports so little "weight" that they become effectively insignificant. As long as you aren't doing anything that's actually against the rules, it won't amount to anything.
There are ten placement matches, though despite the "League" trappings there is still an underlying Elo system, so the system's "confidence" in your matchmaker rating will tend to remain relatively low for some time, allowing for quite a bit of upward mobility early on even if you have poor luck in your placement matches. The matchmaking is pretty decent, though obviously early on when it doesn't "know" you it can be a real grab-bag affair.
Oh yeah, and have fun!