Can I upgrade to game pass ultimate after my current Live Gold Membership runs out?

I have cancelled my Ultimate Pass and I'm happy with 12 months Xbox Live Gold membership I was able to purchase after the Ultimate Pass had expired. My original concern was whether or not I could just buy Gold or would it convert to Ultimate Pass after
previously upgrading to it, as I no longer wanted to use Ultimate Game Pass and just have Gold.

If Game Pass Ultimate is currently active you will need to let it run out before you redeem the Live Gold card otherwise it will like you said convert the membership.

Yes. You can upgrade at any time.

It's better to stack yoir membership you can do so for 3 years max for when you upgrade you want 2years and 11months do when youbupgrade you get 3 years of xgu

Yes, you can cancel Xbox Live Ultimate whenever and revert to only Xbox Live Gold.

So, when it says "Purchase of Xbox Game Pass Ultimate automatically upgrades your existing Xbox Live Gold or Xbox Game Pass membership(s) to Xbox Game Pass Ultimate at a conversion ratio each based on days remaining. Future
code redemptions are also subject to a conversion ratio. Conversion ratio subject to change. All conversions to Xbox Game Pass Ultimate are final: Once converted, you cannot re-convert your Xbox Game Pass Ultimate membership back to a previous membership.",
it means if you activate Xbox Live Gold subscription when your subscription of Ultimate is still active. ¿Am I right?

I think after activating ultimate, if you redeem a Xbox live Gold, it will extend your ultimate subscription.