Create egrep commands using regular expressions that can search a text file in a Linux environment and find answers to questions:

1) Lines in the file with at least a total of 54 characters

2) Lines that have three ds followed by xyz (the ds do not have to be consecutive and the xyz does not have to consecutively follow d)

3) Lines that have a palindrome word of 7 letters

4) Lines that only contain integers which are between 0 and 400