Endnote web and desktop

Hi there I have three questions

1- my endnote desktop recently started to hang every minute I used it, I have deleted it and MS word (MAC) and reinstall both but the same issue keep happing (any suggestion)

2-The I decide to go for endnot we but still another issue

I have sync my endnote desktop library with endnot web.

 Whihle using endnot web and I open any old file where the references was inserted for desktop and I try to ‘Edit library reference’ I get this messages  ‘The reference no longer exists in your library.’ (on the web)

lastly, I have made my own referencing style how can I upload it to be used in my endnot web