Welcome to the support forum This is a good idea, as you will have the views and experiences of others to draw on. It might have been a difficult thing to do, but it is worth it.
When you were 11 you were in a project with friends and formed a friendship wiht one in particular. You knew the project was only for a limited time and stopped that friendship as it seemed as if it was not practically possible to keep it going.
Four years later on life is different, you have as you say 'depression anxiety and crap". Not good. In fact it sounds like a pretty horrible time. I would think it is only natural to look back on happier times -and a happy relationship.
That's OK and understandable. Unfortunately your mental health conditions are not leaving you alone but sending your mind back to those people and wanting to be with them again. This has gone further so now you are wondering about what they might think of you now, which is where all those low self esteem thoughts generated by depression and anxiety kick in. You wonder if you are hated, even though there is no real reason I can see why you should be.
You kick yourself for ending the relationship even though it was not going to be practical and you really have no idea how it might have turned out.
Can I ask if anyone knows about all this, how you feel and hope? Have you told your parents, or seen a doctor, have you in fact been diagnosed by a doctor and are under treatment?
Trying to get out of a condition, in my case including anxiety, was not something I could do by myself. though I tried for a long time. I really did need medical help, plus I was fortunate in having a caring family too. Now I'm good and my mind no longer goes in circles
You are welcome to talk here as often as you might like