I joined the company in 2020

[mrmvp]

1-I joined the company in 2020, after graduating from high school.
2-I joined the company in 2020, after I graduated from high school.
3-I joined the company in 2020 after I graduated from high school.
4-After graduating from high school, I joined the company in 2020

After the comma, should I write a subject-verb agreement sentence? I think the one and four are more natural with the gerund. one, two and four have commas, unlike three. I think all sentences are correct, but I am not quite sure about using the comma. Thank you.

 

[tedmc]

No commas are required for 1 and 2.
Yes, all four are possible, but 1 is the shortest and most natural.
A comma does not have do be followed by an independent clause, if that's what you mean by "subject-verb agreement sentence" as in 2-4.