Right now, I am using mattermost v11.0.2. If I will upgrade mattermost version, will all the UI changes that i have done will stick their or will i have to do the changes again? And, what about custom plugins?
Depends on how you made your customizations? CSS/JS changes in /opt/mattermost/? Or anything else?
I did change react code. And, some changes in config.json and email templates. Also, made one customized plugin for post message in a channel. Based, on these changes, tell me what things would be impact.
React code will be overwritten, also email templates. config.json will not be affected. I would also suggest to have the config.json read from database. There are docs on how to change this.