Can same creature attack both planeswalker and player, dealing half dmg to each?
Can same creature attack both planeswalker and player, dealing half dmg to each?
Nope. Creatures can only attack at one player or Planeswaker at a time.
how about if it has double strike, can it do one round against the player and one against the planeswalker?
No. Double strike doesn't make it attack twice, it makes it deal damage twice. It's still only attacking one player or planeswalker, it'll just hit them twice.
Fluttershy is best pony.