Hue-Saturation is still available as Colors>Hue saturation. Importing the old one from 2.8 unlikely: 1) I don't think it's a separate plugin, 2) that won't add it back as toolbox icon, and 3) in Gimp 2.10 it is likely quite different (has to work with 32-bit values) .
For closing, the behavior you describe is not in standard 2.8, you have likely added something to 2.8 to achieve this. The "unsaved changes" dialog did appear with 2.8 and many people installed scripts to circumvent it. You can quit Gimp very quickly using Ctrl-Q+Ctrl-D (clsoe and discard everything), no need for additional scripts... Of course you are likely to join the club of people who post here asking for a way to recover layers in an image they quit a bit hastily.
For closing, the behavior you describe is not in standard 2.8, you have likely added something to 2.8 to achieve this. The "unsaved changes" dialog did appear with 2.8 and many people installed scripts to circumvent it. You can quit Gimp very quickly using Ctrl-Q+Ctrl-D (clsoe and discard everything), no need for additional scripts... Of course you are likely to join the club of people who post here asking for a way to recover layers in an image they quit a bit hastily.