A free float rail could be adapted for the SR22, but a two-piece rail would require modification to the point where it would not be considered feasible. A simpler option is to buy the rails which Ruger offers, which attach to the existing handguard with some screws. I'd recommend you put some purple threadlocker on the screw threads when you do this.
Trying to figure out what you mean by foregrip.. if you're referring to the forward heat shield, it could be done, but you'd have to replace the factory heat shield with a free floating one.. IMO, better to just buy the optional Picatinny rails through Ruger and add them. If you mean a Vertical Fore Grip, of the sort designed to be fitted onto MIL-STD-1913 (i.e., Picatinny) rails, then yes, but again, you'll have to get the optional rails from Ruger. If you've misused the term foregrip, and are actually referring to the pistol grip behind the trigger, then the answer is yes.
Let's see... Remington makes a variant of the 700 chambered in .223, I believe the Ruger M77 is available in .223... not 100 percent certain about the Winchester Model 70, but I believe it is or was available in .223. .223 Remington ammunition can also be cycled through rifles chambered for 5.56x45, such as the AR-15, Ruger Mini 14 Ranch (the Target models have a dedicated .223 chamber), variants of the Daewoo K2, Kel Tec SU17, some AK-based rifles, etc.
Contact Sturm/Ruger and ask for an archive check. Sometimes a small fee is involved.
There are a very large number, and a complete list would not be feasible. But some examples can be given. While the .223 Remington is dimensionally similar to the military 5.56x45 cartridge, the two are not the same. A 5.56 rifle may chamber a .223 cartridge - it is not recommended to try firing 5.56 ammo in a rifle with a dedicated .223 chamber.The AR-15 and variants and clones, Ruger Mini 14, and Kel Tec SU16 are some more common examples of rifles which can chamber the .223 Remington cartridge. The ones listed have a 5.56x45 chamber, although Target models of the Ruger Mini 14 have a dedicated .223 Remington chamber.Variants of rifles such as the Winchester Model 70, Remington 700, and Ruger No. 1 have been made with dedicated .223 chambers.
Standard
15 or 25 yards
200 or so
It's worth between $10 to $15 used.
The 5.56/.223 Remington rifles can be. Other calibres cannot be, unless the upper is replaced.
Romance of the Rails - 1912 was released on: USA: 5 November 1912
Colt, Bushmaster, LMT, Stag
Impossible to answer with out a detailed description.