“I asked them what I should use for sealer and they told me no windex, no ammonia, just soap and water. Or I could use 409. I showed them my Texax Pro Sealer and they said that was only for the edges.”

You seem to be talking about cleaning and sealing like they are the same topic. They are not. Regarding cleaning your granite, your installers are correct that Windex or ammonia should not be used for cleaning granite. “Or I could use 409” - you said sealer, but Formula 409 is a spray cleaner, not a sealer. Regarding sealing, it doesn’t make sense that a sealant is only for the edges. Something was lost in the translation, as can be seen by what you’ve written.

Note that not all granites need to be sealed. Some granites are very dense and non-absorbent, and won’t stain, so do not need to be sealed at all.

I asked about sealing. They told me about cleaning. I showed them my sealer. They told me about cleaning. I did Google, and 409 does have a granite cleaner.

Then they told me I could only use the sealer I had on the edges. I'm not making this up. They seemed to think that the sealer I had was only for edges. In fact, they showed me where to put it. Nothing lost in the translation, just inaccurate information being shared by the installers.

I told them that I'd already had to poultice several stains out of my granite and I had not expected my granite to need this.. I have a house full of kids. Had I known I was going to get stains (after I asked about the differences between light and dark granite BEFORE I made my purchase), I would have chosen a darker granite. In my previous home, I had Uba Tuba/Verde Butterfly (not sure which) and Blue Pearl. I thought that all granite never needed sealed and didn't show stains. The laugh was certainly on me! :)

They seemed to think I did not understand the difference between cleaning and sealing. I very well do. Now that my granite is sealed properly (their "sealing" after installation was a joke), I have had no trouble with stains. I shared this so that others would know that the information here on Houzz is right on.