R muffs a punt at his own ten yard line, after a scramble for the ball,(A) k recovers in its own endzone, or (B) the ball goes through the endzone out of bounds. what happens in both those situations?

In a it is a safety because the kick never ended and the force involved is K's kick. 90 yard force play what???

Assuming you mean K's endline in b. the same applies.
It doesn't seem right, but that's the case

Maybe you could clarify something here or at least for me... 'R' as muffed a kick at their 10 yard line and in (A) you are asking what the result is if the ball is recovered by 'K' in their endzone?
You sure you don't mean 'R's endzone? I can't envision the ball being muffed 90 yards downfield into 'K's endzone.

(A) If I may assume the endzone was really 'R's endzone, the result (NF) is that 'K' recovered a dead ball and it is 'R's ball the the R-20 due to a touchback.
(B) touchback.

why is this a touchback and not a touchdown for R?

Jumpmaster. First off if it was in R's EZ it can't be a TD for R can it.
But in either case under fed rules a kick is dead when it crosses the goalline of R. So in either situation (Recover or going over the endline) the ball would be long dead. The force for putting the ball into the EZ is still K's kick, and the result a TB.

Thank you Jim.
Jumpmaster: the play as written is not clear and we tried to clear that up with some assumptions or assertions made to the play.
I was hoping Yankeesan would come back and correct what appears to Jim and I to be confusion over just which EZ the ball is actually declared dead in. As Jim points out, there is no TD for "R" and I'll add no matter which EZ is the correct one.

i am sorry, i meant R's endzone. everyone was right, it was not a 90 yard muff. sorry for the confusion. is it a touchback in both situations?

Touchback in both situations as soon as the ball crosses the goal line since a muff doesn't end the kick.

ahhhh! I forgot the force factor. 2-13-4. Duh.

Jumpmaster keep this in mind. Force is never a factor on any kicks going into R's endzone (2-13-4a). The ball is dead as soon as it broke the plane of R's endzone, so it doesn't matter who caused the ball to enter the end zone.