Hello dear users , I wanna to make some changes in html code of octoprint source code and then install it.
now i have 2 questions : 1- i have installed octoprint on my raspberry pi , i wanna to know that can i inject my edited code to the raspberry with out reinstalling or i must reinstall it ??????
2- how should i reinstall it with new code? i want a precise manual
thanks in advance 
depends on how you changed it. the docs have it clearly shown how to setup and run a development environment for this, and you can run the virtual printer locally for testing.
https://docs.octoprint.org/en/master/development/environment.html
If you have a cloned repo, you can use the download zip URL in Plugin Manager technically to install a custom version, but upon next upgrade it will get overwritten.