Your Q3 indicates that your Virtualbox Additions is not working.
You might not be seeing an error, but everything you describe like your fixed VGA screen resolution and unshared clipboard are related to Virtualbox Additions.
If you create a custom kernel, IMO there is a fair chance that the pre-compiled Virtualbox Guest Additions won’t work.
More than likely you’ll have to compile your own Guest additions which is not usually difficult…
To custom compile your Virtualbox Guest Additions…
- Remove your pre-compiled Guest Additions and all related
zypper rm "virtualbox-kernel*"
- Install c compiler and dependencies(make should already be installed)
zypper in gcc make
-
Mount your Virtualbox Guest Additions ISO.
You can do this ordinarily by launching your Guest, then in your Guest graphic console,
in the menu bar running above your displayed Desktop,
Devices > “Insert Guest Additions CD Image…”
If the ISO is not available, you may have to download from the Oracle Virtualbox website, make sure the ISO version is the same as your Virtualbox version. -
In your Guest open an enhanced console and cd to the following location where “user” is your logged in user account
su
password
cd /run/media/user/VBox*
and execute
./VBoxLinuxadditions.run
Pay close attention to stdout to verify success or if a problem is encountered.
Resolve any problems until successful.
HTH,
TSU