AI content

1. Assets should not be upscaled, as it does not create new information, and the buyer may be able to do that on his side if needed. However, since the rise of generative AI, contributors are using a multitude of upscalers. 
   
   For photos, I would consider raw upscaling, as that is preserving a maximum of quality and it accesses data that gets "lost" as soon as you convert the final edit to JPEG or PNG. 
   
   Upscaling per se is not GENERATIVE AI, even if the tool claims to use AI. I can, however, imagine that some tools will use generative AI to create small details in upscaled assets, details that could not be created by other methods. 
    
2. When you are using generative AI tools to create a picture or to modify a picture in an essential way. There is also new legislation (in some regions) that makes it mandatory to mark generative AI assets. Adobe conforms to this legislation by adding metadata to the pictures. I would guess that the contributor portal also reads this metadata to determine the state of the image. 
    
3. Some companies are banning the use of generative AI assets for use on their products. There is nothing more troubling to a company than getting caught using generative AI to give the impression of real photos. There may also be legal implications, especially for bigger companies. The small, spamming advertisers use generative AI extensively, however.
    
4. No sale, no revenue. An image does not earn you less royalty, even if it has been modified by generative AI.
    

In general, there is no direct penalty for using a specific tool to output high-quality images. The only issue is when you upload generative AI assets and you do not mark them as "generative AI". Here, however, the penalty will be account suspension if caught.

Original or not, AI breadcrumbs are easy to detect. 

Use this online AI image detector to scan your image. 

AI image detector. Detect AI-generated media at scale

3. & 4.  Yes, GenAI can adversely impact search results & earnings. Many Stock buyers deliberately filter-out GenAI content for various reasons. It’s out of your control, so don’t worry about it.

Not sure exactly what you mean by enhancement, but here’s what you might try doing. Go to the site below and submit one of your images. If the result suggest the image is more than a few percentage points (10%-18%), you might consider labeling them as AI to be on the safe side.

https://sightengine.com/detect-ai-generated-images

I agree pretty much with ​@ZALEZPHOTO. But to answer your questions directly:
1. Yes it is okay to use upscaling and enhancement tools.
2. Only tag them as AI generated if all or parts of the image are created using AI. This does not include enhacment. Enhancment can however, fool the automation checking for AI-tags and may get your account flagged.
3. No. Other factors such as MetaData effect discoverabillity.
4. No.  

You’re asking different questions. The main answer is that if it is a real photo and the AI tool only upscaled it (no new elements introduced), treat and label it as a standard photograph.

Why are you upscaling? Keep in mind that over stretching will damage the file and cause a rejection,

That usually happens when photos are too small.

the same applies with denoising and sharpening tools.

My advice is only use if it’s absolutely necessary and keep it to a minimum.

I strongly recommend that you spend some time using AI asking precise questions and links from Adobe Stock addressing your questions.

Cheers!