How do people make regular improvements posted videos on YouTube and other places?

After uploading, only chaning annotations and smaller things (like thumbnails, title etc) will be allowed.
For anything else, the video will get a new URL AND reset views/comments.

If you want to keep the same link, get a URL shortening account, where you can edit the shortening URL.
Please note, this almost always means a subscription service, as the free shortening URL's are a one time thing.

Example free bitly:

bit.ly/12345 links to youtube.com/v/1234
CANNOT edit. therefore, useless since the Youtube URL will change.

Bitly subscription:
bit.ly/12345 links to youtube.com/v/1234
later on, log in, and adjust:
bit.ly/12345 links to youtube.com/v/1234edit
later on:
bit.ly/12345 links to youtube.com/v/1234edit2

You asked, "Is it possible to post a YouTube video in a manner where the link doesn't change as I make improvements to the video?"

The answer is no.

Anytime you post a video a new URL is created.

So you can edit an existing video, as @Kimputer mentioned.

You cannot upload a new video to replace an old video.

Aside: If you have many videos + have frequent updates across all your videos, the solution is self-hosted streaming video.

So you run your own YouTube, rather than use YouTube.

The allows escaping YouTube demonetization/deplatforming + odd/incongruent Ads showing up with your videos.

If I use the Amazon web services to store the video content in a way that the URL would not change, then I couldn't use YouTube's service to promote it.

Would that be accurate?

Will I be able to use other services to promote it such as tick tock (spelling?) or others that I keep hearing about?

1) Using Amazon may or may not work.

AWS tech is download/push tech, so for a handful of users watching a video infrequently, this will work.

If you're targeting 1,000,000s of simultaneous videos playing at once of a $100/month garden variety machine for $0 video streaming code, then you'll use self-hosted, video streaming, likely using PHP + Apache 206 tech to provide true streaming.

2) You mentioned, "If I use the Amazon web services to store the video content in a way that the URL would not change, then I couldn't use YouTube's service to promote it."

This doesn't really make sense... well... unless you just put a place holder video on YouTube with a comment point to real video.

This seems like a lot of work for no real benefit.

And only you know if this actually make business sense in your specific case.

3) Whether you can use other services like Tiktok or not, depends on their current TOS (Terms Of Service), which can change any time.

Remember when Google's motto was "do no evil" + then they removed this phrase from you company credo.

When using 3rd party services (I don't, other than a Machine Provisioner to physical hardware... far away from the US...) at any moment your 3rd party service can change it's TOS zeroing out your income.

4) Recent example.

Working on a project recently, a client was getting free Vimeo hosting, then they changed terms saying... starting in 2x weeks, you either pay $24K/month (yes you read that correctly, that's per month) or we cancel your account.

Ouch.

5) Considering #4 leads to the primary reason for self-hosted video streaming.

You must either keep a very good archive (I do, many don't) of all raw + mastered audio/video clips or rely on 3rd party services to do this for you.

Might seem convenient to do this in the beginning + is all rainbows + unicorns... till you succeed... then torque off some Big Tech Cartel member, which then deletes all your videos.

So real cost of using a 3rd party service is they can put you out of business instantly, so you must be prepared with your library of audio/video content to upload somewhere again.

Or... self-host all your media, so you can ignore this problem

How much will it cost me to host the videos on my Lightsail webserver at AWS?

Will it slow down my site?

Can I make the URL permanent by doing it that way?

Could I then still "promote it" on youtube, venmo, or tiktok?

What I am asking is "What is the best method for promoting a single video that I want to be able to improve over time that doesn't run the risk of being shut down"?

If you don't expect 1TB of traffic, you'll be fine and within your subscription limits (but please do check your contract though, maybe you agreed to a lower limit)

Your site will probably not slow down significantly, after all, Amazon is known to be an excellent CDN. If you host it as a "flat file", you can keep your URL permanent, yes. The (mobile) browsers take care of the playing of the file then, unless you link it to a page with a Javascript player.

Define "promote it" on YT, tiktok etc? Do you mean, just buy advertisement? Of course you can still buy advertisement on those platforms.

If you don't use copyrighted material, you definitely won't be shutdown if you host it yourself on AWS.

Here it is so far https://profitsharingprojects.com/res/carlist.mp4. Now the normal method for me of promoting content on youtube is to post it there but you can't post a URL. Instead, you have to upload a video and that would prevent me from being able to edit the content of the video to improve it which is the goal.

So in this case, what would be a good place to test a trial run at promoting it after it's been edited and becomes a sales-worthy video?