I/you/we/they have sung. He/she/it has sung.
The past perfect tense is had sung.
I/You/We/They sing. He/She/It sings. The present participle is singing.
Sing
"Has been singing" is in the present perfect progressive tense. "Is singing" is the present progressive tense.
The present perfect tense of sang is have sung.
The present perfect tense of "sing" is "have sung" or "has sung."
The present perfect tense with the past participle of "sing" is "have sung."
I/you/we/they have sung. He/she/it has sung.
I sang I have sung is the present perfect tense. You would not say, "I sung the song well."
The present perfect tense of "sing" in passive voice is "has been sung."
The present tense of "sang" is "sing."
The future perfect tense of sing is "will have sung."
The past perfect tense of "sing" is "had sung."
Present perfect tense.
sang, not sung. "I sang a song" is correct, but "I sung a song" is not. You would say "I have sung a song", which is present perfect tense.
The present perfect tense of "exist" is "has/have existed."