Alice, 13 bytes

M%/RM\
d&\tO/

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Input via separate command-line arguments. Reverses the first line (and every other line after that).

Alice, 13 bytes

M%/RM\
d&\tO/

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Input via separate command-line arguments. Reverses the first line (and every other line after that).

Explanation

       At the beginning of each loop iteration there will always be zero
       on top of the stack (potentially as a string, but it will be
       converted to an integer implicitly once we need it).
M      Push the number of remaining command-line arguments, M.
%      Take the zero on top of the stack modulo M. This just gives zero as
       long as there are arguments left, otherwise this terminates the
       program due to the division by zero.
/      Switch to Ordinal mode.
t      Tail. Implicitly converts the zero to a string and splits off the
       last character. The purpose of this is to put an empty string below
       the zero, which increases the stack depth by one.
M      Retrieve the next command-line argument and push it as a string.
/      Switch back to Cardinal mode.
d      Push the stack depth, D.
&\R    Switch back to Ordinal mode and reverse the current line D times.
O      Print the (possibly reversed) line with a trailing linefeed.
\      Switch back to Cardinal mode.
       The instruction pointer loops around and the program starts over
       from the beginning.

Alice, 20 bytes

/RaKQ
\iO%@w /dn$@d&

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Reverses every other line from the end (i.e. the last line is always reversed, but the first one may or may not be, depending on whether there's an even or odd number of lines in the input).

Alice, 13 bytes

M%/RM\
d&\tO/

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Input via separate command-line arguments. Reverses the first line (and every other line after that).