A lot of us "experienced" quilters are slow to change our rotary blades. Then, when we finally do, it's such a relief to have the fabric cut easily again.
When your table knife has more of an edge than your blade, it's probably way overdue. :? Seriously, when it becomes an effort to cut the fabric, it's probably time to change the blade.
Sometimes one can get good deals on blades on e-bay. Be sure to compare prices elsewhere so you know what your top bid should be.
There are so many kinds of hand sewing needles available. A lot depends on what you want to use them for. Another of those "it depends" questions.
Yes, there is a difference from brand to brand. Some are much easier to thread than others. Some glide through the fabric more easily than others.
Ask away. As you've probably already noticed, you will get a variety of answers.
If you get two out of three that agree, you will probably be okay with that advice.
Exception: Wash your fabrics before cutting them. (My strongly felt opinion)