Statistics or suggestions for garrote?

How would you handle a PC who wanted to be a shapechanger dragon?

Could you build a long ramp with Stone Shape?

If you had a Ranger Beast Master w/a Giant Poisonous Snake & they came into contact w/ Yuan-ti would it be immune to the charm ability?

In D&D if you see one raptor then the ones hidden in the bushes are automatically spotted too?

Any advice for a 15 y/o first-time DM?

What do you feel is biggest ‘DM crime/sin’?