Questions about different campaigns...

Can u use weapons and items from other campaigns if u dont have the other campaigns? Like I have prophecies only but can i buy a sword that originates from factions and still use it (and what if they have inscriptions?) Also if I use a trial key and in that trial I get a few skills can I still use them on my prophecies account when the trial is done?

Yes you can keep/use items from other campaigns (both stuff u get from trial keys and by buy from other players).

No, you don't keep skills you unlock from trial keys.

Technically you keep the skills, you just can't add it to your skill bar until you own the campaign. As soon as you buy it its yours to use again.