If opponent uses hidden blade on my unit, and I respond with reaction star cross on my unit and another opponent unit, do I draw 2 anyway?

To answer your question directly: No, you do not draw 2 cards.

When your opponent plays Hidden Blade, it targets your unit at a battlefield. When you respond with Star-Crossed, the chain resolves in reverse (Last-In, First-Out). Because Star-Crossed removes your unit from the battlefield (returning it to hand) before Hidden Blade attempts to resolve, your unit is no longer a valid target for Hidden Blade.

Sequence of Events:

1. Opponent plays Hidden Blade, targeting your unit at a battlefield. It is added to the chain.
2. You play Star-Crossed in response, targeting your unit and an opponent's unit. It is added to the top of the chain.
3. Chain Resolution (LIFO):
   • Star-Crossed resolves first: Your unit and the opponent's unit are returned to their owners' hands.
   • Hidden Blade attempts to resolve: It checks for its target at the battlefield. Because your unit has been returned to your hand, it is no longer a legal target at a battlefield.
4. Result: Per the rulings on Hidden Blade (see RiftJudge FAQ #5879 and #9309), if the target is no longer at the battlefield when Hidden Blade resolves, the spell cannot identify "its controller," and the entire draw effect fails. No cards are drawn.

This interpretation is consistent with Rule 359.3.e.12, which states that if a target becomes illegal or changes location such that information like "its controller" cannot be determined, that check returns "null," and the resulting instruction is ignored.