90 days from receipt date. Your question about a later receipt date. Did you mean Notice date. It doesn't matter what the notice date says.
It's the receipt date that matters. That will be on your notice the USCIS sent you.
For the interim EAD it does NOT cancel out your EAD application . You get the interim until they approve or deny the application still pending.
BUT YOU ARE IN MOTION TO REOPEN YOUR CASE. They will not issue you an interim in this case.
You can not legally continue to work.
From Murthy.com
Chat User : If I-485 is denied, can I continue my job once an MTR is filed within 30 days? Is it legal? I do not have any other visas.
Attorney Murthy : A person is not legally allowed to remain in the U.S. based simply on the filing of an appeal or an MTR. Only if and when the MTR is finally approved, is the person considered to have maintained status in the U.S. Otherwise, the individual is deemed to no longer maintain valid status and this could jeopardize the ability to obtain the GC approval down the road. Depending on the reasons for the I-485 denial, it may be worth speaking with a knowledgeable immigration lawyer to consider other available options. For example, it may be possible to refile a new I-485 with an I-140 to avoid accruing unlawful presence and also be able to obtain an EAD and an AP for the principal and all derivative family members. Did your lawyer discuss that option with you? If not, you need to consult with a good lawyer who may be able to help you. If you do not have a lawyer, then you are welcome to contact our Office to consult with us and consider options before settling in as the MTR being the only option available.