I don't know how mechanically capable you are, but many times small
engines just don't have the power to really chew themselves up. It
isn't like a V-8 where you have seven others pounding on the stopped
one. I'd try; put thin oil in the crank case, atf would do, then fill
it with penetrating oil through the spark plug holes & let it sit for a
couple of days (leave the spark plugs out). Then try turning it back
and forth with a wrench a little at a time. If you begin to gain a
little, stay with it till you get full revolutions. Once it begins to
turn easier spin it with the starter till it turns easily by hand with
the plug still out, drain the crankcase change the filter and refill
with your regular oil, replace the spark plugs. If you are lucky it
should start and run now, if you are really lucky it won't knock or
smoke.