Can I work after my work permit application approved but waiting for EAD card to arrive?

No, working while your OPT is approved but you're waiting for your EAD is illegal and can jeopardize your legal status in the US. You can't start working until you receive your Employment Authorization Document (EAD) card and the authorized start date has arrived. The EAD card will state the dates you're authorized to work.

Can I start working after my OPT work authorization approval but before I receive the EAD Card?

No, you cannot start working until you receive your Employment Authorization Document (EAD) card. Even if you have received a notice of approval for your Optional Practical Training (OPT), you must wait until you physically receive the EAD card before beginning employment. Working without the EAD card is considered unauthorized employment.