The past perfect tense is had collected.
collected is past participle of collect.
The past tense of collect is collected.
Present perfect is formed with --- have/has + past participle.Because collect is a regular verb the past participle is verb + -ed = collected.So present perfect is have collected or has collected egHe has collected his pay.They have collected the rubbish early today.
"Has collected" is the present perfect tense of "collect" used for third person singular subjects.
If you meant what is collect in past tense, It is collected.
Existed is the past tense. The past perfect tense is had existed.
The past tense of "bleed" is "bled." The past perfect tense of "bleed" is "had bled."
The past perfect tense of hope is had hoped.
The past perfect tense of "submit" is "had submitted."
The past tense of sit is sat; the past perfect tense is had sat.
present tense past tense future tense present perfect tense past perfect tense future perfect tense present progressive tense past progressive tense future progressive tense present perfect progressive tense past perfect progressive tense future perfect progressive tense
The past perfect tense of 'get' is 'had gotten'
"Had been" is the past perfect tense of be.