is my lawnmower beyond redemption?
In my estimation (and bear in mind i'm no mechanic) your engine is seized up, and do you really want to spend half your summer rebuilding a mower engine? You have two options:


Take it to a small engine repair shop and get an estimate. Diagnostic services vary but will generally be less than $100. If the cost of repairs is less than a new mower, maybe its worth fixing. If not see point 2.
Hold a tasteful memorial service in the back yard, say some kind words about your late mower, and then buy a new one at your earliest convenience.