In addition to the other good recommendations, I would include 'R'. It is a great numerical platform with excellent graphics capability and can be downloaded from:
https://www.r-project.org/
R has numerous free numerical and plotting packages for many different applications, see:
R is an open source free computing system that, when combined with the 'RStudio' GUI interface, provides an excellent computing platform. RSTudio can be downloaded from:
https://www.rstudio.com/
A search on YouTube will bring up many R tutorials.
For general purpose. Actually for undergraduate lab/practical course "Numerical analysis for engineers".
Originally, I was use matlab and mathematica occasionally for this types of work but want to know some package program/tools for specifically numerical analysis work. such as Interpolation, regression, differentiations, integration, partial differentiation, ordinary 1st order, 2nd order partial differentiation, solving linear non linear equation etc (methods: newton, rungi-kurtha, euler, raphsion and so others) @Chama.
These are exactly the type of problems i used to assist one professor at uct. We use matlab. We familiarise the students with both build-in function, such as ode45, and also write down their own code. So i thing u need software that has advanced buiild in function and that can also allow the students to edit their own program.
Many excellent options have been already mentioned. I would like to add SageMath:
https://www.sagemath.org/
SageMath is a free open-source mathematics software system licensed under the GPL. It builds on top of many existing open-source packages: NumPy, SciPy, matplotlib,Sympy, Maxima, GAP, FLINT, R and many more. With SageMath you can access their combined power through a common, Python-based language or directly via interfaces or wrappers.
SageMath mission is to create a viable free open source alternative to Magma, Maple, Mathematica and Matlab.
Masud Ibn Afjal , for some of problems you cited above, we have a C++ library called Trilinos (https://trilinos.org/). If you want to implement your own program and if you would like to work with large problems, you can use it.
Another option is MATLAB. It has an easy language and lots of numerical analysis tools (or Octave, if you don' t have access to a Matlab license).
For symbolic languages, I suggest you Maple and Mathematica. You can use symbolic language in MATLAB too, but I think Maple and Mathematica are better.