finished writing

English as a Second Language English Vocabulary, Grammar and Idioms
1
  1. Have you finished writing that novel?
    1a. Have you ended writing that novel?
  2. I have finished my job.
    2a. I have ended my job.
  3. They have decided to end their affair.
    3a. They have decided to finish their affair.
  4. He is elder to me.
    4a. He is older than me.
    Please correct all.
    Thanks.
2

1, 2, 4, 4a are the correct forms.

3

Beeesneees,
3. They have decided to end their affair.
3a. They have decided to finish their affair.
You haven’t given answer for #3 and #3a?
Is it #4 correct? or it is meant for #3?
Please confirm.
Thanks.

4

‘… end their affair’ is the correct one.

Informally, it would be quite common to hear
‘They’ve finished with each other.’ / ‘They’re not together any more. They finished last month.’ and similar phrases, but this is special use of finished, and it does not apply when related to nouns such as affair and relationship:
Their relationship ended.
Their affair ended.
Their marriage ended.

5

‘… end their affair’ is the correct one.

Informally, it would be quite common to hear
‘They’ve finished with each other.’ / ‘They’re not together any more. They finished last month.’ and similar phrases, but this is special use of finished, and it does not apply when related to nouns such as affair and relationship:
Their relationship ended.
Their affair ended.
Their marriage ended.