05AB1E, 32 31 23 bytes

.•VvÈ©•¹∍¬„ v:Rηε¬ý}.c 

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-1 thanks to Kevin Cruijssen and -8 thanks to Adnan

Explanation (Stack example w/ input of 3):

.•VvÈ©• # Push 'aibgyor' | ['aibgyor'] ¹∍ # Extend to input length. | ['aib'] ¬ # Push head. | ['aib','a'] „ v: # Replace with ' v'. | [' vib'] R # Reverse. | ['biv '] η # Prefixes. | ['b', 'bi', 'biv', 'biv '] ε } # For each.... | [] ¬ý # Bifurcate, join by head. | ['b','b'] -> ['bbb'] | ['bi','ib'] -> ['biiib'] | ['biv','vib'] -> ['bivvvib'] | ['biv ',' vib'] -> ['biv vib'] .c # Center the result. | Expected output.