It's not difficult to select the first or last row - that's just a case of ordering your inputs and using SELECT TOP 1:
SELECT TOP 1 * FROM MyTable ORDER BY MyColumn ASC
Will give you the first, and
SELECT TOP 1 * FROM MyTable ORDER BY MyColumn DESC
will give you the last.
In your case however, it may not be possible at all because you have no column on which to sort - and if you do not specify a sort order then SQL is at liberty to return rows in any order it sees fit - and that order can change between two successive runs if SQL decides to reorganise it's tables for greater efficiency.
I think you need to look at adding a column to your table which "date stamps" each row according to when it was created to allow you a positive ordering mechanism. If you don't, then any other solution which works at present may fail randomly in the future, with potentially harmful results.