Form N Fit 1-1/2 in. White Plastic Slip-Joint Sink Drain Tailpiece Extension Tube

Only true if you want a plumber to custom fit your drain line. PVC is more permanent than the old chrome covered bronze which I have changed many. PVC does not rot like the old fittings did.

Under the collar with the flat side of washer against the collar and tapered side towards the pipe going inside.

Probably not. Made to do slight curves - up to90°. To make it to your drain pipe, you will need 2 smalls or one long, which Home Depot doesn't have.

Yes

Under the collar with the flat side of washer against the collar and tapered side towards the pipe going inside.

If it is easy accessible I would. Just so you can monitor it. Like most removable pieces, it will need to be visually accessible to know how it functions. If it is covered or impeded by anything, I would not.

I keep seeing them come up as discrepancies on inspection reports when a house comes up for sale. My speculations run the gamut. Might be a national code. Might be a viral myth amongst inspectors. Every inspector I know are knowledgeable, so the myth is unlikely. Regardless, I don't use the flexible couplers. A complete plastic drain kit is cheap and provides a fresh start. I always get extra parts too, extensions, elbows, tailpieces, and always a flexible coupler just in case. Whatever you don't need you can take back, but you don't have to make a special trip if you're short. Try not to open the packages. If a flexible coupler is before the trap, that would be crazy unsanitary with all of the pleats for stuff to hide in, accumulate, fester, smell, open to the indoor atmosphere. After the trap, the next guy is exposed to unnecessarily gruesome developments. You don't want to be the next guy. If it's being used as the trap, that's just begging for clogs. Replacing the entire drain system under a sink has become the easiest, even a fun project to do. Don't tighten everything up until everything fits just the way you want, be conservative in your cuts, test rigorously, tighten everything again in a week. Hand tightening with a tiny amount of tool torque does the trick. Don't overtighten. If as I ponder it's likely to be national code, it's because there are much better ways to do the job, cheaply and easily. Home Depot selling the flexible couplers regardless gets a bye from me. They can make a great solution for someone who has painted themselves into a corner, need a universal solution handy, or need a temp fix to get by. It is better than a leaky drain. Works well regardless of skill level. Every municipality I've dealt with defaults to the national code for plumbing, and electrical and all revisions thereof. The pleated, flex couplers are probably out of code no matter where you live.

Yes it will.

Yes it can smell as the food decomposes. If after the P-trap then you will not notice this but if before the P-trap you may notice some odors as the food rots.

If the drain is 1-1/4" tubular size then this would work.