If you're referring to an area, you say 'at'; "I want seats right at the front". But if 'the front' is an enclosed space (as in a car) "in" is right.
PS for advanced students: "the front" has a specialized meaning in a sea-side context. So prepositions that collocate with "the front" include "on": "We lived in a lovely little cottage right on the front."
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