Skip step in Kodi is the preferred navigation method. When playing video the left/right direction arrows do small jumps and up/down direction arrows large jumps if no chapter markers exist, and jump chapter markers if they do. More information can be found on Kodi’s wiki… https://kodi.wiki/view/Skip_steps
If your equipment is setup with CEC working the OSMC remote is configured to send a Kodi CEC suspend action if you long-press the home button when on the main home screen. This is the only screen in which it will send that signal. In order for suspend action to actually do something you would need to navigate to `settings>system>input>peripherals>cec adapter> and set “TV” on the “devices to power off during shutdown” setting. More information on the remote can be found here…
If your AVR does not have support for decoding any particular format then enabling passthrough for it will either give you no audio or a horrible sound you don’t want to hear. I would recommend reading through the following guide which should clarify most questions in this regard…