I am wondering if anyone can help me, please. Are all the records for all the parishes in Dublin online or not?
I am talking Catholic, Protestant, Presbyterian, C of I, etc.
If not which ones are missing or destroyed?
I think the answer to your question is too long and complex to fit into a post on RootsChat.
Putting Dublin parishes online is a work-in-progress, as you will see from a link in heywood's reply.
2 experts who keep a finger on the pulse of developments in Irish family history are:
Claire Santry of Irish Genealogy Toolkit
http://www.irish-genealogy-toolkit.com/and John Grenham of Irish Wizard.
They both blog frequently.
A list of existing C. of I. parish registers is on the RCB Library section of the Church of Ireland website. A new edition of it was published recently. An internet search for Church of Ireland Parish Registers Table should find the latest copy.
GENUKI website which has information about churches including year of foundation and register runs, is organised by place. Search for Genuki Dublin. It's a volunteer site so coverage of each place depends on the volunteer. It has maps with colour-coded markers for churches.
Sean Wilson's website is another for finding church locations. swilson.info