posted by Henry2 .
I left out the following sentences. I really don't know which alternative is best.
1) Influenced by Lord Henry’s words on youth and beauty, he is terrified of aging (ageing?). He fears that he will lose everything when he loses his youth.
2) He impulsively vows that he will kill himself when he grows old and wishes that the portrait could (would/might?)grow old (age?) in his place whereas he remains (stays or would stay) young.
3) Dorian’s wish about the painting introduces the Faust theme, which Wilde develops throughout the book. (The Faust legend was well known to Wilde through popular culture.)
4) Faust, legend has it, sold his soul to the devil in exchange for knowledge and power.
Ageing is British English and aging is American English spelling.
2. would grow old / or / would age
The other things in parentheses are also possible in #2.