Can a D3 ninja answer this question

Adventure mode/campaign question.

-I got my wife to finally play after YEARS.
(I’ve been playing since launch)
-The plan was for her to do campaign to learn basics and then make a Seasonal char and we’d occasionally play together blahblah…

-she beats campaign as Crusader.
Then starts adventure mode.
-after a discussion she agreed to make a seasonal char
And she creates a WitchDr and likes how it plays different etc.
She played till level 30 when I finally woke up.
-I noticed she’s in adv mode but still doing campaign (/odd)
-So I tell her to go to act3 top Right to get Kanai Cube
And she can’t travel there or anywhere in act 3.
**My thinking is OMG maybe you haveta complete the campaign with every character to unlock adventure mode free travel…
—BTW—I/she could leave game and pict the act in settings and start there but it all has to be explored…
Someth8ng NONE of us have done in years since we long ago made out characters…
—sorry for long post. It kinda weird and ackward to even word the question.

Tldr when a 1st time char is made in seasonal/adventureMode does one still haveta go
Through campaign to unlock.

Sounds like in Campaign mode and not adventure.
Must have Reaper of Souls Expansion in order to play adventure mode (noted below)
Season Characters do not have to beat Campaign in order to play Adventure mode. However, when season ends, won’t be able to play in adventure mode unless a nonseason char has unlocked it, just like any character right now that is non season. Its kinda glithcy of season char beats campaign and when season ends if it unlocks adventure mode for nonseason mode. Might have to beat Final Boss again when season ends. So if you did beat Campaign mode in Season, dont delete that Character.

Kanaii cube and Ruins of Sescheron are not part of Campaign mode. The map to get it is only on adventure mode which is only available if have Reaper of Souls expansion.

Once cube is gotten, all characters in that game mode Season Softcore has the cube unlocked. Season Hardcore will have to do Cube run also to unlock for all characters in that game mode.
You cant change cube powers or get the cube in Campaign mode; however whats nice though, when you get cube and put powers on a char and switch to campaign mode in same game mode (nonseason vs season) the powers are still active in Campaign mode.
So if season char that didnt have to do campaign can go get cube, put powers in, get powereled leveled, geared and so forth can now go to Campaign mode and have all the powers in cube as well as being pretty OP and do Campaign mode really easily.
Note: for nonseason could also ask in chat for someone to unlock Adventure mode by them opening Act 5 final boss.

Holy Retard Alert!!!
She was on Campaign and not Adv mode…
Ugh!!!
— when I originally to,d her she was on campaign and not Adv Mode she stated she was in Adv Mode…
I just figured ya only got ‘The Fog Of War’ lifted off you completed campaign with that character/class and was desperate to find a fix as I didn’t think she would do it again… sorry guys…

*on a funny note I’ll share a quote she made.
“Why is level 30 Witch Dr more powerful then my level 70 Crusader”??
Haha
I’m just glad she stuck with it and played 12 hours today.

Thanks for replies everyone.