I don't think this is currently possible out of the box.
1) Added the information where this is set up (in the battle system's settings).
2) Target highlights are only available when selecting a target for an action.
You can probably do something with
Interaction Machine components, they have
Mouse Enter and
Mouse Exit start types that you can use to highlight and stop the highlight.
3) Check out
Group Target Settings or
Individual Target Settings in
Battles > Target Settings.
Unlike the regular target selection (for the target of an action), they let you target a combatant and automatically use actions on it. Group targets are for the whole group of the combatant, individual targets only for the combatant that selected it.
4) You'd probably need to write a custom cursor handling or use schematics for that.
5) Same as
#1, calling the battle menu via input key is set up in the battle system's settings for the system you're using.
6) Battle menu can't be shown like that - but you could bring up a menu screen or choice dialogue when using interaction machines for cursor enter (see #2).
7) That's tricky ... when using control maps, that could be possible, but if you're using the battle menu and not have a group/individual target selected it'll bring up the regular target selection.
8) Same as
#6.