Is there any advantage in solving questions in a non-standard order in normal div2? In div4, div3 and div2 edu it's obvious that we gotta go from easy to hard as it reduces time penalty. But in normal div2 it's hard to tell. For example score for a 1500 question decays way faster than that of 1000 or 500 rated ones. So I am assuming there is some benefit in attempting those first?

I think generally going from the easiest to the hardest is the most optimal.

I know 2 strats with weird solve orders:

1) Skip the problems you are stuck at and return to them later. Sometimes I was solving in order BDAC. In my experience it is extremely effective.

2) Solving contest starting from E, and skipping the contest if you dislike the problem, if you have not sent anything you rating wont be affected. It is probably effective, but kinda unethical and very stressful imo

What's so unethical about the second option?

Because I think if you participated in the contest, it should be rated for you

What about unrated participation?

Well, you can calculate it yourself, taking your average solving time per problem, and using a little bit of math. The loss for A per minute is 2, for B is 4, for C is 6 and so on. As a basic example, if you are able to solve all problems in slightly same time, like 2-3 mins for a problem, then It's beneficial to start from the hardest(hardest you can solve).

Or don't waste your time on these shenanigans and practice instead, going greedily A -> B -> C -> ...

where did you get this info of 2 4 6 split? Is it accurate?

Here

So as you say,we should try the questions with higher points?

see problem C for 5-10min, if you have absolutely no idea then you should skip the contest. Because if you cannot solve C then almost surely you get negative delta and lose of score for AB by late solve about 5-10min is absolutely nothing compare participating contest which to fail to solve C. same rule applied as your rating increasing blue for D.