I have a button on Lightning Record page. On click i am redirecting to a LWC. Is there anyway where i can redirect or open the LWC in a full screen page. As of now it is opening with salesforce main header.
I am afraid that this is not possible. The header is static content of the general LEX. While you maybe could do it via css i would not recommend it because it can break at any time when salesforce changes structure / their own css.
Potentially you could also serve it via a Visualforce page and adress it this one instead which can be displayed on an own full page - but not sure if lightning out is worth the price.
i would just keep it as is to be honest
You can create a lightning application and open it in Lightning without the standard header.
An app is a special top-level component whose markup is in a .app resource.