Who chooses to develop a character in offline mode will not have any possibility to use the same character to interact in online mode at any time ??

If there is no possibility to use character developed in off mode to online mode, what are the biggest differences between modes?
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There could be the possibility to perform offline campaign mode and connect online when necessary with the same character. :(
I really enjoyed the game, but I didn't want to feel censored in any way for choosing to start offline. Since character development takes hours and many days of play. I say this for reasons of internet connection instability during the game.

Thanks for this beautiful game