so I land with Final Reserve, but without Alternate fuel - is this still legal?
Naturally - yes! If you had to divert (go to an alternate) then obviously, you use some of your Alternate Fuel - which is what it is carried for. Therefore, after landing at alternate - the fuel has done it`s job and you have arrived at the alternate or second alternate.
Many, if not most, if not all, carriers also include a `navigational` amount of fuel
addition at approx 5% plus another 5% (I forgot what this second 5% is for, but I am sure you will enlighten me) = totalling 10% of total carried on top of your, taxi, t/o, climb, step, cruise,
diversion, descent, appr,
G/A,
divert lo alt, hold/island holding, taxi, and is added to any SOP additions that the airline requires for their particular operation as stipulated by the local Civil/Federal Aviation authority/administration and of course, ICAO, who as you know have recently amended a document on minimum fuel.
All of this is not taking into consideration ETOPS which as you all know requires a much larger amount of fuel to be carried as per the ETOPS requirements subject to a particular operation/route/dist from land over the sea/ocean.
Holding fuel - and (for remote out of the way exotic locations) Island Holding fuel - (although this was not part of the question above).
. . (don`t forget enough fuel for wing relief loading + whatever your company wants in your tanks at destination)