Magic bow and damage reduction

Just started "The Mud Sorcerer's Tomb" with my group, and we had several questions regarding rules.

Is there any news on weather magical bow passes through damage reduction in dnd next, like it did in 3.5 E?
I didn't play 4E but it would seem to me arrows fired from magic bow should ignore "non magic weapon resistances".

Also, while I am here, how does critical work. Are martial dices and sneak attacks also automatically maximized?
Can rouge use his skill dices advantage on tricks  (and get advantage on that die on his saving throws as well)?

Oh, and does price determine availability of an item? If an item costs 5000 gold, can i place it in "very rare category" even though it is not "magic item" ?

So many unclear rules here, but generaly i like the setting  

I don't think magic automatically bypasses anymore, since they've mostly replaced DR with resistant/vulnerable, which are very specific about what affects them.

A good thing in my opinion, since after a certain point in 3rd edition non-magical damage reduction became completely useless.
In older editions of D&D you need special magic arrows to penetrate "resistance to non-magic weapons." In 3.5 and 4th edition, bows give their resistance piercing to any arrow that you shoot. So its safe to assume that in the playtest you do not need special magic ammunition.

I am pretty sure Martial Dice are maximized on a critical hit. You never use your skill die for a saving throw, as far as I know. When you spend your skill die on a skill trick, that means you cannot use it to boost your roll in some cases. If it says to use the number you rolled, then yes you roll twice.

Generally I treat the 500 gp armors as +1 armors, uncommon. I treat the 5000 gp armors as +2, and that makes them rare. I would be very hesistant in giving out those items as the monsters aren't designed to fight against them. 

Thanks for input guys. I appriciate your opinions.