Questions #1

What are the types of strings in python?
Depends on the version of Python. In the second branch, two types: single-byte strings and Unicode are represented by the str and unicode classes, respectively. Python 3 has one kind of string, str, which is Unicode. There are no single-byte strings, instead of them there is a bytes type, that is, a chain of bytes.
Is it possible to change a single character within a string?
No, strings are immutable. The replace, format, and concatenation operations return a new string.
How to concatenate a list of strings into one? How to split a string into a list of strings?
To join, you need the .join() string method. To split, the .split() method.
How to encode and decode strings?
Encode - translate Unicode into a byte string. Call the .encode() method on a unicode object.
Decode - recover Unicode from a string of bytes. Call the .decode() method on a str or bytes object (Python 2 and 3 respectively).
In both cases, explicitly pass the encoding, otherwise the one defined in the system by default will be used. Be prepared to catch UnicodeEncodeError, UnicodeDecodeError exceptions.
Comment out the expression 'ABC' == u'ABC'
Strings are compared by character codes. If both strings are typed in Latin, their codes are pairwise equal, and the resulting strings are also equal.
If at least one letter is typed in a Russian character, then the lines will not be equal. For example, the Russian letter A has a code different from the Latin letter A.
Remember that characters from the bottom of the ASCII table have the same codes in any encoding.

Lists, tuples, dictionaries, sets

How is a list different from a tuple?
At the language level, they differ in that you cannot add or remove an element to a tuple. There are no differences at the interpreter level. Both collections are represented by an array of pointers to a PyObject structure.
For a list, functions are defined that add a new element to such an array, remove an existing one, and merge two arrays into one. They are called by the list methods .append(), .pop(), .sort(), etc.