I'm building a home on a fairly significant slope. Rather than using stilts/pillars, soil from the upper-side has been plowed lower to create a flat space in the middle for pouring the foundation. So now, there are three levels: 2 sloping and 1 flat.
Concern 1. The "wall" height between the top and middle levels where the soil was removed is probably about 10-12 feet high. It looms behind where the house will be built. Is there a chance of mudslide? Do I need a retaining wall?

Concern 2. The height from the first level to the second level is even higher, but it slopes somewhat steeply. Since the soil of this slope was moved there, Im worried the foundation could slip because the earth is less dense. Do I similarly need a retaining wall between the first and second levels to reinforce the soil where the foundation is located?

Thanks!

We might be decent construction people but you surely need an engineer. Is there a chance of mudslide? Do I need a retaining wall? All of your questions are serious and need to be addressed by professional people. Who permitted the foundation work? Who is doing the site inspections? Don't go any farther and risk your investment or worse your life. Look at Colorado.