*Is it better to swap 6 & 7 ?1.PV-move of the principal variation from the previous iteration of an iterative deepening framework for the leftmost path, often implicitly done by 2.
2.Hash move from hash tables
5.Killer moves (non capture), often with mate killers first
6.Non-captures sorted by history heuristic and that like
7.Losing captures (* but see below
*) Depending on the implementation, the board representation, whether and where SEE is used, the extension policy (recapture extensions) and other stuff - many programmers favor losing captures before other none-captures - directly behind the killers. They are kind of forced, and one possibly has to deal with all kind of tactical motives and interactions, one may not consider in move ordering. Such as pins, batteries, discovered attacks and overloaded defenders. Otherwise, obviously losing captures are likely refuted cheaply. But if a losing capture fails high for some reason, we have saved the effort to generate, and more importantly to search other non-captures at all.
*should I use SEE instead of MVV-LVA to order moves at PV nodes ? and if so should I use it only for captures or should I use it for all moves ?
*where should "Threat Move" be placed ?
2-how do you score capture-promotions using MVV-LVA , and where should non capture promotions be placed (see 1) ? same for enpassant moves should they be ordered by MVV-LVA or should they be ordered using history , killers ...etc ? and where to place them (see 1)?
are these techniques good in theory bad in practice , or why does most engines refrain from using most of them ?Less common techniques
These techniques are well known theoretically for non-captures, but not all programmers use them:
•Countermove Heuristic 
•Last Best Reply
•Butterfly Heuristic 
•Threat Move from null move refutations
•Enhanced Transposition Cutoff (ETC)
4-Is there any techniques that shouldn't be mixed ?
5-should evasions/PVnodes/NonPVNodes/QsearchNodes be ordered differently ?