As the others alluded to, since you can't find a rule specific to these FTs, the restrictions are the same as for any player who is not on a marked lane space. The only difference is all players are off the lane.

Just so I'm clearly understanding: Behind the three point line extended, right? Thanks for your patience.

Corrected for you.

With Badnewsref's correction, yes. Behind the three point line and the FT line extended. And, the restrictions are only in place from the time the shooter gets the ball until the try ends or the ball hits the rim or backboard.

Thanks everyone! Watch out, confidence growing... :)