Some information about Interactive Grid I found useful:

https://hardlikesoftware.com/weblog/?s=cookbook
The APEX IG Cookbook by John Snyders - an extremely useful set of examples. At this (20.1) time of writing, 19.2 was the latest available version of this cookbook, but you should be able to find the latest version using the link above.

https://github.com/mgoricki/orclapex-ig-cheat-sheet
It's called a Cheat Sheet, but Encyclopedia would probably be a better title :-)

https://ruepprich.wordpress.com/2017/03/09/apex-updating-interactive-grid-cells/
Updating Interactive Grid cells.

https://thtechnology.com/2017/07/03/apex-interactive-grid-javascript-basics-cheat-sheet/
Javascript and Interactive Grid.

https://www.foxinfotech.in/2019/10/oracle-apex-interactive-grid-get-selected-rows-example.html
Interactive Grid Get Selected Rows Example
Note 2024-01: site seems to be down, so using the Wayback Machine: https://web.archive.org/web/20230130203902/https://www.foxinfotech.in/2019/10/oracle-apex-interactive-grid-get-selected-rows-example.html