Q.Soil crust
How to deal with crusted soil in a container? And can I add leaf manure as a mulch while seeds are in germination process?

If your seeds are germinating and you try to mulch now your can risk disturbing the seeds.
You may want to do a soil test to see what is causing the soil to have a hard surface and what would be the best additions for your soil.
Leaf mulch can be an ideal organic material for gardens.
Your local County Extension office can help you with a soil test.
https://www.gardeningknowhow.com/extension-search/
Amending the soil is best prior to planting for best results with your plants.
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/improving-garden-soil.htm