Found info that should explain flex and how many prime time games you can play.
Begins Sunday of Week 11
In effect during Weeks 11-17
Only Sunday afternoon games are subject to being moved into the Sunday night window.
The game that has been tentatively scheduled for Sunday night during flex weeks will be listed at 8:15 p.m. ET.
The majority of games on Sundays will be listed at 1:00 p.m. ET during flex weeks except for games played in Pacific or Mountain Time zones which will be listed at 4:05 or 4:15 p.m. ET.
No impact on Thursday, Saturday or Monday night games.
The NFL will decide (after consultation with CBS, FOX, NBC) and announce as early as possible the game being played at 8:15 p.m. ET. The announcement will come no later than 12 days prior to the game. The NFL may also announce games moving to 4:05 p.m. ET and 4:15 p.m. ET.
Week 17 start time changes could be decided on 6 days notice to ensure a game with playoff implications.
The NBC Sunday night time slot in “flex” weeks will list the game that has been tentatively scheduled for Sunday night.
Fans and ticket holders must be aware that NFL games in flex weeks are subject to change 12 days in advance (6 days in Week 17) and should plan accordingly.
NFL schedules all games.
Teams will be informed as soon as they are no longer under consideration or eligible for a move to Sunday night.
Rules NOT listed on NFL web site but pertinent to flex schedule selection: CBS and Fox each protect games in five out of six weeks, and cannot protect any games Week 17. Games were protected after Week 4 the first year of flexible scheduling, but are now protected after Week 5; however, they are back to Week 4 this year, probably for the same reason as that first year: NBC hosting a Christmas night game and the other games being moved to Saturday.
Three teams can appear a maximum of six games in primetime on NBC, ESPN or NFL Network (everyone else gets five) and no team may appear more than four times on NBC. At this writing, no team is completely tapped out at any measure; five teams have five primetime appearances each, but all of them have at least one game that can be flexed out. A list of all teams’ primetime appearances is in my first two posts for Weeks 4 and 5. .