Other than Lock, across all age groups I've played almost every position at some point in time.

Fat kid = Prop, but could also run a bit, pass and had ball skills so doubled as Hooker when necessary.

Skinny & fast teenager, who also played football and lots of other ball sports. So rotated between FB, FH, and occasionally even on the Wing.

Went pretty heavy on learning skills and bulking up as a young man, so moved into Centre for a decent few years at both 12 & 13.

But then tried to play at a higher level and found I was nowhere near big enough, fast enough, etc. However, I could pass, kick, and had loads of endurance, so was given a shot at SH instead.

I bloody hated it though. Even your best game was never good enough because you invariably did something wrong, which pissed off some monster Lock or Front Row lump, and spent the next few weeks getting battered in training for it.