not sure where to post this hence adding here.
how to run in this full screen mode even when the screen is locked. As far as I looked, it’s only live activities that the developers are made available with. Is there a way to create our own UI on lockscreen, given a similar usecase exists?
There's no supported way for you to create a full screen, Lock Screen experience with the APIs currently available. If you'd like us to consider adding the necessary functionality, please file an enhancement request using Feedback Assistant. Once you file the request, please post the FB number here. If you're not familiar with how to file enhancement requests, take a look at Bug Reporting: How and Why?