As far as I know' I don't think is possible to unlock the TV without a remote control. You can buy a replacement remote control for the Sinotech TV STL-24VA3. Check here https://www.pricecheck.co.za/search?search=sinotec+tv+remote+control&category=869
we can also help you hunt the original remote control for your TV if you can tell us the remote control model number which should be printed either front or back of the remote control. You can comment below for more.