Applying H4 for my wife while my H1 is in process?


I am on F1 OPT currently and it ends on Feb 2019. My employer applied my H1b this April and my petition is still in process. My wife lives with me in the U.S on F2 visa. My employer did not include my wife in my original H-1 filing. I have below questions 1) Does she have to leave the country after my H1 gets approved. If yes, what is the grace period? 2) Can my employer apply her H4 cos now since my H1 is still in process? If yes, Will it get approved along with my H1 or does it take longer? 3) Lets say she immediately went to India after my H1 is approved and wants to come back on F1, in case if her F1 gets rejected will it also affect her chances of getting a H4?