Effectively, and expecting to be able to hit your target, you'd be looking at about 25 metres, under ideal circumstances. The bullet may travel significantly further, but most of your 6.35mm pistols are "pocket pistol" designs, intended only for the closest of ranges. As far as how far the bullet will travel, it may travel up to 500 metres or more, under the right circumstances.
25-65 USD
Small handgun
small .22 or .25 caliber handgun
S&W never made a 25 ACP handgun for retail sale.
No published sn data.
50-200 or so
AFAIK, none. There were one or two importers in FL that sold 25 ACP pistols.
10-1000 USD depending on specifics
As long as it's the correct caliber, yes.
The short answer is no. The longer answer is, you may be able to get a .25 cartridge into a .22 caliber gun, but it will likely jam and be very difficult to get out, and if it fires, it will probably damage the gun and possible the shooter. The .25 has a larger diameter than the .22.
$25 or so. Low value handgun.
No. A smaller caliber will either not fire at all, or will split the cartridge casing if it does fire.