1. Runtime exceptions occur during execution of the program and they exit abruptly in between. Compile time exceptions are those that are found before program executions start.
2. A regular expression, regex, or regexp is a sequence of characters that define a search pattern. Usually this pattern is used by string searching algorithms for find or find and replace operations on strings, or for input validation.
3. Here's a description of the Linux commands:
   • head: used to see the first N number of lines of plain files.
   • tail: used to see the last N number of lines of plain files.
   • cat: used to see the content of plain files.
   • awk: AWK is a programming language designed for text processing and typically used as a data extraction and reporting tool. It is a standard feature of most Unix-like operating systems.
4. Following is the answer:

def append(source, destination):
    with open(source, "a") as fw, open(destination,"r") as fr:
        fw.writelines(fr)
append(source_file_name1, file_name2)

5. Following is the answer:

filename=input("Enter file name: ")
for line in reversed(list(open(filename))):
    print(line.rstrip())

6. The output for the expressions are as follows:
   1. C@ke
   2. Cooookie
   3. <h1>