[Grammar] Talkig about unspecified past time

[Ab.m]

If i'm talking about completed actions at an unspecified time in the past, should i automatically use the persent perfect ? Or only if it's describing the present result of completed action ?
Second question : is it possible to use past simple with an unspecified time period ?

 

[Matthew Wai]

1. I saw it before.
2. I have seen it before.

I think both are possible.

 

[jutfrank]

If i'm talking about completed actions at an unspecified time in the past, should i automatically use the persent perfect ?

Absolutely not.

Or only if it's describing the present result of completed action ?

Yes.

Second question : is it possible to use past simple with an unspecified time period ?

Absolutely.