Are All Champs Available In AR URF?

No. It's what you have plus Free Rotation (like ARAM). Some players make accounts too roll that select few they want to play.

But forget that question. It's up the whole patch! You're probably gonna get to play what you want unless you own every champion!

Are they playable, yes... are they all free, no. You have to own whatever it is to play it or have it on free week.

Only One For All had all champions enabled for free.

I haven't seen Sona or Ryze once.

Seems like I never see a sona, lux, or any support or mage for that matter. All I ever get or go against is a team with a trynd, shen, Udyr, kayle, cait, riven, xin, mf, or garen and I somehow always reroll into one of the ones I listed. Oh and dont forget how we never see any mages or ap carries like xerath lux and many other mid laners.