 Re: 4 questions
Okay, okay, okay...
Firstly, there is no time marker in each of the sentences. Therefore, they are incomplete.
"By this time next year, you will have learned English" is fine, for example.
It is okay to use "english learned".
The third expression is fine but rather informal.
Now the last expression, again, needs a time marker.
Remember that the present perfect tenses links one event from the past with a recent/present event. Well, future perfect (and future perfect continuous) links a past event (the reason for a past participle to be used - "been" in your example) with a future event.
So I need a time marker to make sense of your example. Here:
I am learning English now.
I have been learning English for 3 years (I started learning English 3 years ago).
I will have been learning English for 4 years next February (Started in the past the event - learning English - covers a period of time that will end in the future).
Remember that all perfect tenses consider time (physical or emotional time).  |