present perfect tense
1.What's the difference between "I loved you " and "I have loved you"?
2. When I use “I have loved you", do I still love the person or not.Just wanna know the meaning of the line from the movie Theory of Everything," I have loved you. I did my best." It's the words of Jane Wilde.

Question

present perfect tense
1.What's the difference between "I loved you " and "I have loved you"? 
2. When I use “I have loved you", do I still love the person or not.Just wanna know the meaning of the  line from the  movie Theory of Everything," I have loved you. I did my best."  It's the words of Jane Wilde.

Answer

I loved you in the past
But I have loved you means I just loved you at this point in time

Answer

1. I think, "I have love you" means, that I loved you, but enough, now I don't.
2. If you need to leave a boyfriend.

Answer

I agree with you. Another example: I worked at that company - I worked there in the past, but not anymore. I have worked at that company since 2014... Express past and present with a connection about something that still happen.