Your second question, I have problems with, first of all you use a
curve, this is not an irregular shape, then you find the surface area
using a formula that you do not explain, and it is not your example,
it is copied from someone else. The leaf also does not appear to be
your example or calculations. My question says to pick an irregular
shape of an object, draw or take a picture of that object and also
explain how you would calculate its surface area and volume, that is
not what you have done.

Question 3 also is not adequate. The question specifically talks about
integrating methods. Completing the square is not an integrating
method, it is a method to solve quadratic equations. You have also
provided 2 examples of completing the square (which do not appear to
be your own) and there isn’t any integration in sight, so I am afraid
that you have not answered this question properly either.
Re-read the questions carefully, and the marking criteria. Provide all
that is asked and you will get full marks, otherwise it will not
happen. Also make sure that any examples you provide are your own