Now for real info:
1) There is no original R4i cards, all of them are clones. R4i Gold 3DS just has official wood support, but other manufacturers have hacked that version to work on their cards a very long time ago.
2) R4 SDHC Dual-Core 2015 will work just fine, it won't need any additional support since DS games are not released anymore.
3) You will never have to update it, DS flashcards are not blocked anymore.
4) Don't bother with DSTWO unless you want crappy snes/gba emulators.
5) The only real difference between R4i Gold and R4i Dual-Core is RTS support on Gold but its not very good.
EDIT: 5 depends on Dual-Core version, there are 2 types of them...one uses Wood menu and other uses TTmenu which will have RTS and it'll be much better than Gold version of RTS.
1) Right, but I think that most manufactures don't have hacked the latest version and hacked versions don't have features like Real Time Save.
2) Yes but R4i Gold 3DS will work well, too.
3) Right.
4) The Emulators of DSTWO aren't really crappy for the average user. Who is really bothered by some almost not noticeable framerate drops?
5) The Dual-Core has RTS as well (as you EDITED) but it's RTS is real crap with a very low compatibility. In addition to that, The Dual-Core's menu is extremly slow and it has some stupid features ("Energy Saver" which turns your screen off after some seconds) as well as just 4 skins or something like that (might have been 6). It just feels like crap.
Before you judge me: I have all of the cards: R4i Gold 3DS, DSTWO, Ace3DS+, R4i SDHC Dual-Core 2014 (it's the same like 2015) and Gamecard 3D (uses hacked wood like the Ace3DS+).