Does the size of the stem adjustment depending on wether or not it is planted contained by a greenhouse or a garden? ...
Answers: Stem size will change as the plant get bigger and needs a thicker stem to accommodate a more developed xylem and phloem for fluid and nutrient transport. A plant will not own a thicker size just from man in a garden or a greenhouse; but a greenhouse may be more conducive for the plant to thrive and grow faster than within a garden because you have better control of the environment that it grows surrounded by.
yes and no. If all else is equal (water, soil, light) after, no. It is easier to regulate them in a green house. Try planting pip in your garden one and the same time you transplant a plant from a green house. At maturity they will be equal.