I am planing a trip to Spain from April 18th to April 28th, 2019. I currently reside in USA. I am an Indian National with H1B visa. My Visa stamp is valid until mid, 2019 and my work authorization (I-797) is valid until Feb , 2020.

Before I apply for the tourist visa I would like to confirm the requirements:
1) Am I eligible to get a tourist visa for Spain if I plan to return to USA on April 28th as my visa stamp is valid until May 16th , 2019?
2) If my travel dates change after applying for visa, do I have to re-apply?

Thanking you for your response in advance.