In volleyball, the following actions are legal for a player:
- Spike the ball: This is a common and legal action in volleyball.
- Cross underneath the net during play: As long as the player does not interfere with the opponent's play, this is typically allowed.
The other actions listed (touching the net during play and hitting the ball twice in a row) are generally against the rules.
So, the legal actions from your list are "spike the ball" and "cross underneath the net during play."