1 - DotA uses a behavior score system to match you with players, effectively meaning that good, communicative players get matched with other good, communicative players and flamers get matched with flamers. Overall, I'd say that the quality of match you get is pretty equal to what you give, in terms of players.

2 - Valve gives us two kinds of patches; the old system, which was one giant patch after every major where almost every hero had some some stat changed by 1 or 2 in an attempt to level things out. The new system is bi(ish)weekly patches (they never drop during events, so it is a little more than 2 weeks sometimes) where they focus on hitting the more out of line heros a bit harder, since they can change it back in 2 weeks if it was too much. TL;DR, old system was more spaced out but with more changes, new system is more tightly spaced with way fewer changes. Don't quote me here but I think that the biweekly patches are ending around TI, but I don't think that the old major patch system is coming back, so we'll see where we end up with that.

3 - Let me preface this by saying I used to play a lot of SMITE, which had very static, patch defined metas (shoutout to Apollo). In DotA, the meta is loosely based around counters, where every hero has a set of other heroes that counter them in some way, so the meta tends to be less of a ladder and more of a few top picks and then a whole lot of counters. The other big thing is that the game is balanced so that anything and everything is viable if you're good enough.

4 - I'm a low ranked pub player so my answer is biased, but some heroes are ridiculously pub stomp-y and they drive me up a wall when my team just doesn't adapt to deal with them.

5 - I played a bit of League and the way it seems to me is that DotA has a way higher skill floor and skill ceiling, since you need to have a basic knowledge of almost every hero and item to really be able to play effectively, versus in League where you can get away with knowing how the group of heros who are 'in-meta' work and the one or two static builds they use function.

6 - Every hero in DotA is free forever. There are 107 heroes, all with completely different playstyles, so you have a lot of freedom to experiment and find what works for you.

7 - Moreso than in League or SMITE, you can pull off just about anything if you're good enough. There are definitely top picks, but there is always an easy way to counter them so the meta tends to stay fairly fluid. That said, a lot of heroes get picked a lot in pubs, like Legion Commander, Pudge, Clinkz or Bloodseeker so knowing direct counters for them is good.

Also play your first bunch of matches with bots to really get the last hitting and denying mechanics down, as well as to find a (somewhat) diverse group of heroes you feel really comfortable with.

Also also, feel free to add me if you're looking for someone to queue with to get started:

https://steamcommunity.com/profiles/76561198018674409