Write a Python program that takes a list of numbers as input from the user, calculates the sum of all even numbers in the list, and returns the result. The program should check if the input is valid (i.e., if it's a list of numbers), and if it's not, it should return an error message. The program should also handle exceptions gracefully and return a user-friendly error message in case of any exceptions.
change_case:capital_word_frequency length_constraints:nth_paragraph_first_word detectable_format:number_bullet_lists detectable_content:number_placeholders punctuation:no_comma language:response_language detectable_content:postscript
less than
HARSH
te
P.S.
Add stress words which are capitalized. Limit those stress words for less than 4 times Write exactly 4 paragraphs each separated with two new lines answering this instruction. The fourth paragraph must start with "HARSH" Include exactly 3 bullet points in your response. The bullet points should be in the form of:
* This is bullet 1
* This is bullet 2
...
 Your answer must also contain at least 1 placeholder (an example of a placeholder is [address]) In your response please avoid using commas response should be entirely in Telugu, no other language is allowed At the end of your response, please explicitly add a postscript starting with P.S.