Hi B C,
Okay, the part in the first picture goes in the upper right corner, under the part identified as the "guide rail for the iSight camera". Thanks to iDoc's [link|https://www.idoc.eu/guides/en/apple/iphone-8-plus/replacing-the-back-cover/544|iPhone 8 Plus back cover repair guide|new_window=true], here's a picture of it in it's proper location.
[image|2775931]
The piece in the second photo goes in the upper left corner, under the part identified as the "Top Left Antenna".
[image|2775912]
Sorry, but I didn't find anything about the last part in your list, but I hope what I did find helps.
Good luck, let us know how it goes!