To answer questions 1, 2, and 3:
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Yes you can ๐
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yep, do your rice. Maybe visit the Unixporn community.
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For the most part (in MY experience) changing DEs only involves installing the desktop package, choosing your login manager, and then removing the old DE and its native apps (unless you want to keep them)
LMDE. Not Ubuntu based, but Debian based so its the closest I can think on the top of my head. It got 32 bit support and Cinnamon desktop.