Will google let me get away with target keyword beside every product name in buying guide?

Will google let me get away with target keyword beside every product name in buying guide? So far it didn't seem to make much of a difference so I wonder if google simply ignores it?

What about captions? Alt tags? I am talking almost grey hat here...

If I've changed the keyword density by like 1%, how long will it take me to see any changes (positive/negative) if I request indexing? A couple Weeks?

I'm not entirely sure, but I think I know what you're talking about. For example, if the keyword is "best face mask" and you write the product subheadings like "best face mask for acne: product name" and "best face mask for dry skin: product name"? If that's what you mean, I've seen other people doing that so you're probably in the clear.