Mulberry tend to have "mitten leaves", lobed leaves. See attached PDF.
Your first photo looks like Carpinus, hornbeam. Though it could also be an elm, Ulmus pumila = Siberian elm, is one possibility. Where this first seedling is growing will help with ID. If in full sun, it could be Ulmus pumila. If it is growing in part shade, it definitely is NOT Ulmus pumila. Siberian elms only grow in full sun. Carpinus, the hornbeams tend to grow in part shade.
The maple I have no strong feelings about. Yes, it is a maple of some sort. It is NOT a Japanese maple, It is not a sugar maple, it is not a Norway maple. But that still leaves a dozen possible different maples.
It is sometimes difficult to identify young seedling plants.