Things I need to know

So sometimes life throws you questions that need to be answered above all else. I am going to present one of those questions to you.

So, in the movie/series The Highlander, sometimes when people die, they find they are immortal, come back to life, and are now part of a group of sword wielding people that don't age and can hear when another one is around by a noise only they hear so that they can get out their swords to cut each others heads off to gain the others power.

My question that needs to be answered, let's say a baby is born, ages about 6 months, then dies of whooping cough or something. That baby ends up being a highlander and comes back to life. The baby is now doomed to live out it's entire life as a 6mo old, no matter how long it lives.

Question 1: being trapped in a 6 mo old body, let's how long do you think it would survive? would other highlanders NOT cut off it's head because the quickening would be small and not worth it, or maybe because they don't believe the baby is actually immortal so they move along and assume the noise they heard belonged to someone they just missed.

Question 2: Let's say the baby manages to survive for 200 years, being stuck in a 6 mo old body, would the baby eventually learn everything like an adult like walking and talking or would it's perpetual baby chemistry prevent it from evolving past that of a 6 mo old?