You know how different ages get labeled (like "terrible twos"), for good or for ill? Well, there's a label for four-year-olds.
They rejoice in their own bodies and brains, such as they think they are. They try things out - AGAIN. They test the boundaries - AGAIN. They can definitely become defiant. What was taught before may need reinforcing now, on a four-year-old level.
Running away when called by a parent is not acceptable in fours any more than it was in twos. Start over again: "When I call, you come. When you go the other way, you don't come back to the park for a while." Then follow through with it. Don't be afraid to.
It will be a definite inconvenience, but at four she needs to experience the consequences of her choices. (That might be good for your younger one to see, too.) Consequences are NOT threats. Threats are making you scared to do something. A consequence is simply what happens when you make a choice. If Mommy drives carelessly, the consequence is not that she gets threatened; it's that she gets a ticket and must go to court. Nobody's sending her to the judge because they're angry and want to scare her; it's simply because Mommy broke the traffic rule!
Actually, children *like* rules - once they see that they're real rules and not just jabbering. There are some rules about playing kindly with other people - including brothers - and not hurting them. Those rules apply to the grabbing and shoving.
If your girl chooses to plays keep-away when it's dinner time, start the meal without her. That's what *you* can choose! When she comes in, she may eat in the kitchen under your supervision. Don't talk much about it. It's just a consequence. You do the right thing, it's happy in the end. You do the wrong thing, you lose out. That helps her learn to make the good choices.
You can tell your daughter that the only secrets she should have right now are what she's going to give her mommy and daddy for Christmas. Doing something in secret does *not* make it all right. Would it be all right if you secretly mixed dog food in her breakfast cereal (or something else that will make her laugh)? No! So her friend went to the bathroom outside? That doesn't mean that she may. Her friend won't even do it much longer - he's probably already learned how icky it is.
Blowing in Daddy's face, besides being unsanitary, is teasing (an mild form of bullying) and is not acceptable. What is a consequence of teasing?
Raising children is always two steps forward, one or two or three steps back. Keep letting your daughter know what the boundaries and the consequences are, in a firm but friendly way, and don't let her get you involved in long intellectual conversations instead of obeying. It feels as if you're starting over, I know, but that's a parent's job, so you get to do it.