I think the general opinion is that you can learn 'trials' type moves on any reasonable XC hardtail. Just put your seat down as much as possible, and stiffen up your front shock.
Obviously a FR type bike or BMX will be better for moves like that but you can do all the basics on a regular XC hardtail. You can do some stuff on FS bikes, but sloppy rear-suspension just makes it too difficult to do much more than basic stuff.