The adverbial forms are spurious, and are falsely formal-- good style is satisfied with 'first, second, third'. If you find yourself having to deal with 'seventeenth', you would be much better served to simply use figures (1., 2., .... 17.) to mark off the points.
If your list is as long as 17, then it would be much better to simply number the list:
1. Apples are delicious;
2. I also like oranges;
3. Bananas tend to get over-ripe before I get round to eating them.
If you are doing a shorter list, say up to four points, then use either "first", "second", "third", fourth; or firstly, secondly if there are no more than two points.
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