Why are these moves considered blunders by stockfish.

Hey guys, in this game I played recently, I felt always had the upper hand, but stockfish points out some mistakes. I would like to know why these are considered bad moves, and if they are decent enough for my level which is ~850 rapid. 

Here stockfish considers the following moves as mistakes:

1) 4. Qb6

2) 12. Qa6

Could someone explain the lines that would be winning for white here, and give an overall game review?

Using Komodo, I see no blunders or mistakes but 2 inaccuracies which are -

4. Qb6

12. Qa6

Stockfish is probably just thinking too hard. Inaccuracy means like it's not a bad move but there are definitely better moves so in this case I agree with inaccuracy? 

Yeah, that is what I mean, but why is it an inaccuracy , and what are the lines leading to white being better. If this could be annotated and shown, It would help, because it is really daunting to go move by move in stockfish, and try to understand the point of each move

On move 4 Komodo was expecting Nf6 to help in center control and development in general and on move 12 Bb4 was best because it would connect the rooks giving them mutual defense.

@1
4...Qd6 commits the queen too soon and obstructs the diagonal of Bf8
12...Qa6? is a mistake. 12...Ne4 was equal.

idk

Then why do you say anything???

I think you moved your Queen too many times and too soon, during the opening phase. You should develop the other pieces first. Like, one of your Bishop stayed to long on its starting square.