My understanding is that any incoming Senior football player is not eligible for a free transfer based on this part of the rule:
b. Students who transfer during the first six (6) semesters, having had the opportunity to participate in three (3) seasons of eligibility of a sport, will be subject to a Thirty (30) day non-competition period or half (1/2) the Maximum Number of Contests, whichever is less, in each sport in which they participated during or after their third year of eligibility, during the Three-hundred Sixty-five (365) days preceding the transfer.
Once you start your junior season, you are locked in. You can transfer once for free at any point up to the start of your Junior season. If you are a multi-sport athlete and you transfer mid-year during your Junior year you would be subject to a non-competition period for any sports that you had already had an "opportunity to participate in".