Can a Child Learn a Foreign Language without obtaining full competency in First language

بچے کی زہنی نشو نما و خود اعتمادی کا گلا گھوٹنا ہو تو اس کو "پہلی زبان" پر دسترس ہونے سے قبل انگریزی زبان کے جبر میں قید کر دیں

I got this comment on the above FB post: 

Actually kids can learn multiple languages early in life a lot easier than later. But the downside is often that they take longer to speak. Girls tend to do better than boys. I learned to speak two and understand a third language all before 3 years of age:

The advantage of parents knowing multiple languages and sharing them with children will ONLY accrue once the child has obtained "full" competency in the "first" language(s) in which parents, grand parents, uncles, aunts, extended family, neighbors converse and the child finds himself immersed after his birth. By full competency I mean that the child can understand a joke, crack a joke, relate a hilarious (make believe) experience that will make family members or friends burst out with laughter. Once a child has this level of competency in the first language, then competency in any other language is a piece of cake. Without this level of competency in the first language, gaining full competency in any other language is wishful thinking.

پہلی زبان
First language is the language in which the child opens his eyes and hear his parents speaking. It is the language with which the child learns to interact with parents, grandparents, brothers, sisters, neighbors and friends. Articulation of thoughts into words and sentences is a complex learning. Then development of verbal skills to express abstract and complex ideas and learning to crack jokes and appreciate humor are the most difficult skills. Once a child has reached this state, learning any other language is a piece of cake.

The friend (Omer Dossani) further clarified that:

Irfan, our servents spoke Bengali, grandparents spoke Katchi, mother and father spoke 40% Urdu and 60% English. So, I cannot relate to what you are saying but maybe you are correct. From the research done by TCF in Pakistan they strongly stand behind their commitment to stick to Urdu as the medium of instruction based on the research that shows that kids learn best in their native language and so far their students are doing well

Articulation of complex ideas requires complex linguistic skills. The added pressure of not having enough verbal skills in a foreign language, stultifies expression of complex ideas, destroying self confidence and impedes mental development. Once complex verbal skills are fully developed in the first language, the child gains confidence to tackle any other language. Eg Schools where speaking in English is must, and the child is being bullied, the child is afraid and hesitant in complaining because the teacher will scold him for speaking wrong English instead of patiently trying to understand child's grievance. The child's emotions get strangulated and destroys his self confidence.