Why would the brake peddle work really hard and the wheels can be turned by hand after replacing the shoes and wheel cylinders on a Kreg Micra?

you power booster could be bad or have a vacuume leak . the power booster is a large round object behind the master cylinder mounted on the fire wall on the driver side . you master cylinder bolts directly to this and you should have a vacuum hose going to this can . this is what make your brake easy to apply.