Show comments on index.php

I’ve tried putting all the codes in comments.php into index.php, but no go.

I find that adding
<?php comments_popup_link(__('Comments (0)'), __('Comments (1)'), __('Comments (%)')); ?>
and
<?php comments_popup_script(400, 500); ?><?php comments_popup_link('No comments yet', '1 comment so far', '% comments so far (is that a lot?)', 'comments-link', 'Comments are off for this post'); ?>
in index.php only shows up while in index and not in individual posting.

I want to have the post (set to show 1 post per page) on index to show together with the comments. Is this possible?

Can anyone help?

TIA.