Without seeing the engine, we'd not know if there's a problem in the assembly.

The engine should be tight when the piston moves to the top of the stroke. See the O.S. Max FAQs about this. It's normal for ABC-type engines.

Usually, a Craftsman #2 screwdriver will fit into the carburetor retaining screws and allow you to remove them. Most American Phillips-type screwdrivers are too pointy, and need to have the tip ground down a bit so that the screwdriver properly fits into the screws.

If the liner's not installed properly, the engine won't draw fuel or run, since the ports won't be lined up correctly.