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Preview does NOT mean to look forward to. Preview means something more like .. seeing something ahead of the normal timeframe. Like a movie preview, which is an advance showing before its public opening. For "to look forward to" - you might be thinking of the word - Anticipate.
The prefix "vision-" pertains to sight or seeing, often related to the eyes or the act of perceiving visually.
The prefix that makes "upgrade" mean the opposite is "down-," so "downgrade" means to lower or reduce in quality or status.
The prefix "ben-" means good or well, so the prefix "bene-" in benevolent makes the word mean something that is kind, generous, and showing goodwill towards others.
The prefix mal means bad or evil.
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the prefix un added to fortunate mean not lucky because fortunate means lucky so adding un makes unfortunate mean not lucky
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Preview
No, a preview is letting you see what it is about.