I've noticed an achievement list with achievements like "Friend in Need" that give me XP and Gems upon completion.
If I will complete them, then will the achievement list refresh with new achievements?
No, there are 11 Achievements:
- 1 for joining a clan
- 3 for donating cards: 25/250/2500
- 3 for reaching an arena: Arena 2,4,6
- 3 for collecting cards: 20,30,40
- 1 for watching TV Royale
However, my personal experience suggests that there will probably come more achievements with updates.
"Hidden Achievements" would probably still be visible as such in Gamecenter/Play Games.
If by "refresh" you mean reset to zero once all are complete - then No, the list will stay completed and you wouldn't get more gems and gold for redoing the tasks, nor will new achievements take the place of the completed ones.
If by "refresh" you mean, if the developers would add more achievements with future updates - then Most likely Yes, but no one can know for sure. Given this is supercell and their other games though, i can speculate this.