[How often do you change your needle?]

I would change mine only if it breaks. 

[Thread is getting caught in hook, breaking]

It's bit difficult to spot the issue. Here is something I found online. I think it will be useful to identify the issues. https://support.brother.com/g/b/faqend.aspx?c=us&lang=en&prod=hf_600_2eus&faqid=faqh00000318_000#:~:text=Make sure the spool of,for the size of spool.&text=The bobbin thread is not,correctly wound%2C rewind the bobbin.

[What accessories to get?]

I'm a newbie here, and was wondering the about the basic items  that I need to start my new project. Is there anything to add in the list apart from these accessories? 

[Perfectly square quilt is not hanging straight?????]

I think the stitched edges are not straight. Try blocking the edges. Probably, this should work.