People who have played POE1 could you answer some basic questions? I am a newbie to this genre, POE specifically.

How does a league function in terms of content?

What happens to our existing characters, currencies, loot?

What happens to our stash tabs? Do they carry over our items that are in the stash or they get wiped clean in the new league?

And is it fine, if I can only build one character every league? Like do I miss out by not playing all the other characters and builds?