There is a bewildering assortment of bits in each kit (Torx, Philips, flat screwdriver, square drive) and there is also a bewildering assortment of assortments. No easy way to select in my opinion; you pretty much have to see them in person to figure out which one is right for you. You may want to consider a five-pack of additional bits for #2 Philips drive screws, since they seem to be extremely common, and my particular assortment had room for some additional bits.
Replacement bits are available in multi packs.
No they are for 1/4 drive impact drivers
I believe so they fit my Bosch and my buddy's dealt As long it is a 1/4 drive