skywards

As adjectives the difference between skywards and skyward

is that skywards is in the direction of the sky, upwards while skyward is pointing or facing at or moving toward the sky.

As an adverb skyward is

at or toward the sky.

As adjectives the difference between heavenwards and skywards

is that heavenwards is upwards, in the direction of the sky or heavens while skywards is in the direction of the sky, upwards.