Dear Rohana,
Welcome to the forum.
There are a number of questions here:
Boiler
Firstly, were you rushed into the new house before the end of January. This is very common and often results in home owners being moved in when the property is not ready and problems with two major systems in the property which should have certification from a competent person i.e. an electrician and a plumber. Do you certification - this will be on the fuse box for the electrics? Did you receive a Corgi certificate for the boiler? If not request one here
Request a Certificate. Once you have this you can get the installation inspected by Corgi
Faulty Work.
Front Door
Good developers will work to the Police Secured by Design standards -
Secured By Design: Doors. Your hasn't and the problem is it is only voluntary and as they say a deisgn flaw. What does the specification say? I am assuming that you have an NHBC warranty, and they do have standards that cover external doors. It sounds like they are trying to implement a low cost bodged solution but it is difficult to say - give the NHBC a ring. I will look it up for you.
I don't think they have to let the residents know who they have contracted to work on the properties.
I hope this helps
Tony