Hi,
I sanded my hardwood floor with a belt sander and it came out very smooth. I used 40/60/80/100 grit paper. I used an edger with the same grits. I also used a hand sander to smooth out some areas that I filled in holes. I made some mistakes and need advice.

I didn't use an orbital sander, so when I applied the stain it wouldn't hold in the spots I used the hand sander. Also, all the areas that I used the edger show through the stain. Some of the floor looks great with nice rich stain, but other areas look very light so the floor looks unfinished

I need to remove the stain, blend the floor and re-stain.

Since the floor is very smooth from my sanding, what grit paper do I need to remove the stain? Do I have to go back to 40/60/80, etc?

By going to 100 grit, did I sand too smooth where the stain wouldn't hold?

Is there anything I could do to help the stain penetrate? I read that using rubbing alchohol helps.

Do I need to use a belt sander, edger and then an orbital sander to remove the stain? Or, can I just use an orbital sander to remove the stain and blend the areas together?

Thanks for your help.

You may be able to do some touch-up, but you will probably have to sand to bare wood with an 80 grit belt sanding grit and then fine sand again.. When the stain has just been applied and is still wet you use a scraper and then hand sand to open the grain and then apply again. Hand sanding with 60 or 80 grit, depending on whether you like a dark stain, before you apply the stain will make a good blend between the edger and belt sander marks. A sharp scraper, one that will make shavings, is less work than taking out edger scratches using only sand paper. I keep a mill file handy to keep it sharp. Sanding with 80 grit along the grain by hand allows the stain to absorb evenly. Sanding with 100 grit on the belt sander will not be as smooth as using a hand sander with 100 grit, so stain absorbs differently according to how open the grain is. Wetting the floor with water and letting it dry before staining,"popping the grain" will help diminish machine marks, but you color will come out darker because the water opens the grain and the pores are more absorbent.
Finish belt sanding with a paper that you dull just a little by rubbing a 60 grit paper across the belt gently while it is running to dull the sharp grits, leaving a smoother paper. Some guys use a steel wrench to slick the paper a little when staining dark.
To make less scratches when using the edger you can use a nylon pad to cushion the paper between the edger disc and the 100 grit sand paper. Or you can finish with a 100 grit sanding screen with a wool disc. If you don't buy your paper at the right place they may not know what you are talking about when you go to purchase either soft spacer disc or the screens.