Can I use this “Concern Weed Prevention Plus” (see photos) on my lawn but not on bare spots, then afterwards plant grass seed on the bare spots? Or should I do it the other way around? The instructions say to use both in spring and fall. Thank you.

I am not familiar with this product. The package should contain instructions on where it may be used. Corn Gluten meal is usually applied in the spring to stop crabgrass seed from germinating. Lawns should be fertilized in both the spring and fall. Grass seed is best applied in the fall. Spring is also possible as a second choice. Go to: https://extension.umn.edu/lawn-care/fertilizing-lawns, for more information.