Level 14 can be proved impossible in its current state, by considering the the grid as a graph with a vertex at each rune and an edge between each pair of adjacent rune. Each edge must contribute exactly 1 to the value of one (and only one) of the vertices it connects, so by replacing the runes with numbers (yellow=0, green=1, red=2, blue=3, pink=4), the total sum of the numbers must end up exactly equal to the number of edges.
In level 14, the layout of the grid represents a graph with 32 edges (16 horizontal, 16 vertical), but you expect us to achieve a target image that has a sum of 33. Clearly not possible.
If any of the three green runes in the top right quaddrant of the target image changes to a yellow, the level becomes solvable. Presumably this should be the one on the top row of the image, since that gives the grid a symmetric "pinwheel" design.