@sh!va I think Your answer is correct but your explanation about the linear grammar is wrong.
According to Wikipedia, Linear grammar is a context-free grammar that has at most one non-terminal on the right-hand side of each of its production.
This production S -> aSb has no problem but S -> SS is not a linear production as in the right-hand side of the production there are two non-terminals.
On the other hand, context-free grammar doesn't have such issues. The right-hand side of the production could have any number of terminals and non-terminals but left-hand side must contain only one non-terminal.
If you find anything wrong, please correct it.