With {Hellrider} effect can u redirect it to a planeswalker?
Yes
A planeswalker can be targeted by any ability or spell that targets a player. You must declare which player or planeswalker you are attacking as attackers are declared.
To elaborate further, the controller of a spell or ability may choose to redirect the damage dealt to a player to a PW that player controls.
Example. You can't {lightning bolt} a planeswalker. You can, however, redirect the damage dealt to a player targeted with said {lightning bolt} to a planeswalker they control.
RESOLVED
To elaborate even further than that, each attacker is a different trigger so you could do some damage to the walker and some to the player with an all out attack.