In ANH we got a concise explanation of the Force. We found out it involved focus and channeling it with your feelings. It also involved training and development.
This is true. So since this had already been established, you can't really hold it against TFA for not establishing it.
Not true at all. We find out that (at least) the dark side can be used to warp either space, time or both in order to freeze animate objects, we see psychometry used for the first time on film, we see the Force assert itself. There's actually a stunning amount of exposition on the Force considering it had already been well-expounded upon in the OT and PT.
Because it doesn't take training to do things with the Force. This was "old canon," it is "new canon," and it is common sense.
As I've posted numerous times, Rey taps into the dark side both times she overcomes Kylo. i don't know why this is so hard for most people to see and/or why it's being ignored. It's a very big deal and no one really wants to deal with this fact. But that's why she's effective when she's afraid. If you watch closely, those times she's afraid, her fear turns to anger. And we all know what happens when that happens, right Yoda?
No, it doesn't. It only contradicts success tapping into the Light Side.
My opinion, those are true, true and false, but all debatable since exposition is such an open-ended word.
The First Order arose from the ashes of the Empire following the Galactic Civil War. So there's actually more exposition in TFA on this topic.
True, ANH did reveal this, but certainly you can't hold it against TFA that TFA did not reveal it since it had already been revealed. But to do tit-for-tat, in TFA, we learn important details about the galactic government that are not revealed in ANH, for instance its location.
Kylo Ren helped the First Order destroy the New Jedi.
The First Order is led by Snoke and during TFA, he gives the order to destroy the sitting galactic government. I'd call this an equally "shaking up on government," wouldn't you?
There is no evidence of any star systems that are loyal to the First Order in TFA, thus, they are clearly not in controlling power of anything either.
Rather than get such a boring David and Goliath style story, we get a much more interesting three-pronged conflict in TFA: An aggressive, well armed First Order that rules nothing, a wimpy, demilitarized Galactic Republic that rules everything, and a ragtag group of resistance fighters who have to hide their location from The First Order and their financial backing from the Senate.
We know every bit as much about the Resistance as we did the Rebellion. We know every bit as much about The First Order as we did about the Empire. We can go fact for fact if you want.