How to reset EFI password?

Question

Passwords

It so happened that my MacBook Pro Retina 2015 was blocked for me. First, the user was blocked, and then the password appeared on the BIOS itself. Now I can't rearrange the OS and get admin access, only the "standard" user. I have already tried many options, but I just can’t reset at least some password. I was offered to reflash the chip, this option will help me 100%, but then the license will be merged and I will not be able to use iCloud.
What can you advise me? Are there options to renew the license after flashing?
ps The laptop was bought by hand through eBay, so I can't present receipts and all documents to the official representative of Apple to prove that this is my laptop :(

Answer 1

Once I did according to this instruction and everything turned out. I don’t know how relevant the method is https://m.habr.com/en/post/250347/

Answer 2

The procedure for resetting the firmware password is performed in an authorized Apple service - https://locate.apple.com/ru/ru/
To prove the purchase, you just need to provide information about the transaction from the same eBay or from PayPal.
Offhand, the situation looks like that your computer is tied to MDM. If this is a normal MDM, the administrator knows the public and private IP of the device. If so, you need to resolve the issue with Apple. There have been cases when devices added to DEP were shipped by mistake. In any case, the problem is solved with the service or support. If this is not done, there is a risk of a serial ban and access to iCloud-related services.
There is an option to contact an unauthorized SC, but you have already described the possible risks.