it's hard really identify the sizes but at least 6.  Yes you can get 2 mani - depending on your nail widths you may have to trim a couple but you will definitely have enough nails.

The easiest way is to wait until the nails begin lifting slightly from the bottom edges. At this stage, you can apply nail glue and reattach them if you desire to keep them on. If you want to remove them, take a a piece of dental floss and slide it under the bottom of the nail, pull it up the sides of the nail, tightening by pulling upward. This gently separates the adhesive from the nail with minimal trauma. Remaining adhesive can be rolled off, then the nail gently buffed.

I have had them last two weeks and longer. I would suggest wearing gloves when you do the dishes or similar activities. If one does loosen up, or come off, you can use nail glue to reattach it. I think they are a pretty awesome hack to getting a shellac manicure. Even if they only lasted a week, you would be at least $20 ahead. You can file them down, or even clip and then file.

They are medium-length for an average size, oval nail bed.  With my hands, which are about 6 to seven inches long, there are only two sizes I am unable to use, between my 10 nails. The smallest, too small for my pinky, and the largest too big for my thumb.  There is a sizable variety and range that can be custom-fit to the individual nail length and depth.

yes.  I don't have large hands so there are quite a few nails I cannot use.

They will last longer if you apply nail glue before you put each one on.

Aloha, I usually file to fit the nail. BUT, the Dashing Diva Nails are NOT for Slim or tin y nails. I've found them to be too wide and much prefer the Impress Press-on Brand, Nail Bliss or Kiss Nails. They fit better.

These do not harm your original nails. I leave them on for 1 week. I peel them gently back using my thumb nail, working top to bottom and back. Very easy