What are my options incase if gets denied ? Can i come back to USA ? Can i fly from Mexico to India ?

One time visa waiver form is called I-983 Form(Costs 585$ at any POE locations), which can be used only once during your entire stay in USA. Incase if you accidentally cross US to Mexico without passport or any documents, you can use this 1 time visa waiver. The same form can be used at Matamoros POE incase if your case ends up in Denial (or ) if your case is taking more time to resolve 221g & you don’t want to wait in mexico for long time (either due to your current job thing or your family is back in US & you need to meet them).