as above, 5 years down the line is going to be your main stumbling block regardless of being let down on dates. new home snagging is done before you move in, you sign off to say your happy with it.
you then have the warranty period with the housebuilder themselves to get any further issues resolved (shrinkage etc), usually 2 years (one rather large housebuilder in particular is now offering 5 years apparently….) and anything after that comes under the NHBC.
obviously i can’t tell how persistant you were at getting the items sorted once you’d moved in, but you should have been on the phone day in day out, until it was resolved. it was there problem and if you werent happy with the issues you had with the house, they should have sorted them for you.
5 years down the line, anything could of happend.
I hope you get it sorted, but i really wouldnt hold out much hope of getting the developer to sort it now. think you may be better just sorting it yourself and moving on. developer would likely wriggle out of it in a small claims court due to timescales and proving issues have existed since day one.