[tenous]

Now they're asking me for the gift card receipts or a picture of the physical cards or an email or sms from the person who "gifted" them to me.

Judging by your post, they've given you four options.

Would that be correct?

Do you think faking the receipts would work or can Amazon cross-check/verify them?

For verification purposes, there's every chance the receipt will be cross-checked.

They said if I don't have the receipt I can upload a picture of the physical cards (which don't exist because they were e-gift cards), or an email/sms of the person who sent me the gift cards. So yes, there are 4 options but the last 2 might not be sufficient.

[mothered]

They said if I don't have the receipt I can upload a picture of the physical cards

The corrupted file method Is something to consider.