1.
It is developmentally normal for small children to struggle with impulse control and to hit, pinch, push, grab etc.
But the experience of being hit, pinched, pushed, grab etc is painful at any stage of development.
When another child is doing these things to your child is can be incredibly triggering and hard to navigate (esp if the other parent is not intervening and is a friend or acquaintance).
Remember that these are moments to teach your children 2 things:
1. Body ownership and permission to set boundaries with people who hurt them
2. That you care about their pain and will calmly but firmly protect them from people that are using hurtful hands or words
Teach your kids to ask, "Is this okay?" and look for a clear and enthusiastic yes, even if someone seems reserved or quiet, to ensure that all affection is confirmed and enthusiastic.
The myth that comforting your child will "spoil" them is not only emotionally harmful but also creates an altered brain state that leads to higher levels of stress and mental illness in adulthood, giving them compassion and comfort will only help them develop a healthier brain function.
The most helpful way for a child to understand boundaries is to model it for them, and as parents, we should also honor some of our children's boundaries as well to protect connection and safety, not power.