Check the "Obtained from" tab next to "Comments" on this page; it lists the Conditions that your character must meet before the "Chat" option becomes available when interacting with Tachros.
Note that when presented with the Crossroads, the options that appear ingame will trigger the corresponding quests.
For the 3rd and 4th Crossroad it is as follows:
[Crossroad] Let's Talk About This = [Balenos] [Crossroad] Gobs and Gobs of Help
[Crossroad] Abandon coexisting with Goblins = [Balenos] [Crossroad] Death to Gobbos
[Crossroad] Old Chief's Parting Gift to His People = [Balenos] [Crossroad] The Aged Chief's Last Gift
[Crossroad] Black Stones Have a Time and Place = [Balenos] [Crossroad] Save 'Em for a Rainy Day
Same advice for the "Grusha's Whereabouts" knowledge entry.
Thank you @Gil. So for this knowledge, you have to choose "[Crossroad] Abandon coexisting with Goblins" and "[Crossroad] Black Stones Have a Time and Place" when it pops up in your screen.
But if you wanna check whether you choose the right one or you did it in the past and check whether you took those in right order or not, open the Quest Tab (Click O) and switch to "Main" tab. Then uncheck "Hide Completed Quests". You will see "[Balenos] Breaker of Chains" series and when you look the quests you have done, you will see the crossroad quest names do not show as you choose but as "[Balenos] [Crossroad] Death to Gobbos" and "[Balenos] [Crossroad] Save 'Em for a Rainy Day".
So verify if you character took in correct order, then go to the NPC that gives the knowledge and took it.
For future new players or new content; I am gonna take note about which character took which crossroad quests in what order.
J'ai beau faire tout comme indiquée, rien à faire. Essayé avec 3 reroll différent. Il faudrait avoir confirmation de la possibilité d'acquérir ces connaissances sur consoles, ce qui est mon cas.
If you're still not getting the knowledge although you did both crossroads as described here
which is:
[Crossroad] Abandon coexisting with Goblins &
[Crossroad] Black Stones Have a Time and Place
in the updated version of the storylines,
don't forget you also have to talk to Tachros afterwards - only the dialog with him (with the same character you did the crossroads with) will give you the knowledge finally.