Create NFT with self-built smart contract or OpenSea

I want to create a NFT collection that has enables me to also launch upgrades in the future. OpenSea seems to be the easier way forward to initially mint the NFT collection however I have some doubts on long-term sustainability. My question would be now:

  • Can I offer upgrades for the sold NFTs at a later stage when I minted via OpenSea?
  • Can I link the NFTs at a later stage with other applications (for example a metaverse game)?

Maybe somebody has experience and could provide some insights here. Many thanks.