Can approvals be revoked

Hi guys My uncle owns a amazon liquidations warehouse and has a lot of new return stock he wants me to sell. All items have been checked brand new return reasons were not faulty or have any defect Theres many things here with lots of monthly purchases when I have been researching the ASINS for each. Now my question is, some items are obviously only sold by the brand and they might not want me selling it also. How do I know which I can sell and which are best not to. Im applying for approvals on a few things and have some concerns, can the permission to sell be revoked by the seller after its been approved/auto approved by Amazon, What is the rules for items sold by Amazon and where Amazon is the cheapest seller. I feel like buying those that Amazon already sells might not be the best idea, wouldn’t want them as a competitor, does their system automatically mark down prices from competitors? Im looking to essentially slightly beat the cheapest competitor. My margins would be a lot more favourable so I can afford to drop prices. I don’t have huge amount of each stock either maybe at most 50pc so my plan is to sell various SKU’s and send them all together. If someone can clear up how the invoices would work. I can probably get from the warehouse but not sure if this is even allowed or will be accepted Would appreciate any insight and advice on how I can go about this, appreciate it