Sadly I couldnāt find answers to these, so Iām here to ask you guys. Maybe you know more than me.
Stat reset -> Only available with 50$ pack? Will there be an ingame option to reset those? Or I can easily screw up my character and say bye bye to it?
Shinobi class -> Dex, Str or what is the main stat for that?
Thanks for the answers. 
The Stat Reset Potion cannot be obtained in-game.
Yes, the 50$ pack is the only pack containing the reset potions. And if its anything like the CBT, there should be reset scrolls/potions? In a shop that probably require TP coins to get.
Seeing as Shinobi comes from Swordsmen, best probably doing Str though having Dex is good for crit, evasion and hit. So both are good! 
If source needed 
I read that part, but this doesnāt mean that there wont be an option for that. Thatās why Iām asking that if there is an NPC for this or anything.
Seems weird that you canāt buy that in the shop.
Well, ācannot be obtained in-gameā means through cashshop or NPC/drop. Maybe IMC is keeping this option for events in the future, who knows =)