Yes it is complete, no it does not include a buffer or spring- and is rather pricey IMHO.
using a buffer retainer
On the AR15/ M16, the spring is retained by the buffer. The buffer is retained by a pin located at the lower outer edge of the extension tube.
The bolt carrier would not return, another round would be chambered, and you'd likely have to replace a bolt carrier, buffer tube, buttstock (if using a fixed buttstock), and buffer spring (if the spring was in the extension tube). You could also cause injury to yourself if the bolt carrier ended up going through the back of the extension tube.
The HK 416 Pistol and Rifle are both the same in construction. the lowers are the same also. It is a scaled version of the HK 416/417 model (.223) only a dedicated .22 rifle. the place the Buffer-tube inserts is capped for pistol specs. But yes a buffer tube from a full length 416 .22lr should work. Be aware that by putting the Buffer-tube WITH a stock constitutes a short barrel rifle and is illegal unless you pay the ATF the $200 tax stamp and process the request to own through them.
Places to go for a complete season of Bones include, Amazon and eBay. They have all the season available to buy. Other options include You Tube, Net Flix, Watch Bones and Fan Pop.
Complete
It rubs the lotion on its skin, or else it gets the hose again. I don't Know.
Stripped lower is just 1 piece of aluminum without the trigger, springs, safety, buffer tube, stock, grip, etc. It is the bare bones you need to begin a custom build; to make it range-ready you will need a lower parts kit, trigger pack, buffer tube, buffer and spring, and a stock.
Green top tube
Pretty easy. Taking off the standard stock from any brand of airsoft M4 is almost the same. First, you need a small L key (the size of the L key depend on the brand) and a long + (plus) screwdriver (about 12 inch or so). First, pull the length adjuster of the stock to the max then slide the stock off the buffer tube. Unscrew the buffer tube cover with a small L key. If you see inside the buffer tube, you can find a big screw. Unscrew it. It's quite long and need some effort. Then, pull the buffer tube off your airsoft M4's lower reciever. Voilla... you've done it!
No. A standard AR15 has a buffer tube that runs inside the stock that contains the recoil spring.
Not very much, unless if you use a metal buffer tube.