Does the Wx at your ALT still have to satisfy the "planing minima" when airborne?
No. It's very simple, once airbourne forget about "planning minima." Just put it out of your head, "planning" minima are always left on the ground.
Or is it enough with actual minima?
Yes. Once you get airbourne you can plan to land anywhere you like, once you
a) have the required (actual) minima to commence/continue an approach
and b) have the required visual references at decision altitude/height.
THE ONLY MINIMA YOU WILL EVER USE ONCE AIRBOURNE IS THE ACTUAL MINIMA AS PRINTED ON YOUR APPROACH PLATES.
And if you hold and divert to ALT 1 (below planing minima) , are you required to carry the fuel to ALT 2 + Final reserve (30 min 1500')
Again, forget about planning minima. The bottom line is, you need to land with final reserve fuel (though don't forget, final reserve fuel is useable fuel, but if you use it, you will need to explain why).
If you hold and you have an expectation that on arriving at ALT1 you will find it above actual minima, then you can plan to arrive there and land with only final reserve left. Remember, the two alternates fuel is a paperwork exercise, designed so that if ALT1 falls below actual minima (remember you are building in fat in the planning stage in the hope it won't) you will have fuel to get somewhere else if necessary. But if ALT1 is good enough to land at, this will become your nominated alternate and you land their with final reserve.
The only situation your question might be correct is if you ALT1 falls below actual minima prior to your diversion and you decide to divert their and have a look. In that case, if you didn't have a reasonable expectation of getting in, you would need fuel to then go to ALT2 if the attempt at ALT1 failed. Though I wouldn't recommend flying around having a look at alternates. If you need to divert, find an alternate you will get in at and stick to it.
So remember, all the planning phase stuff on the ground is a paperwork exercise, once you're airbourne the fuel is yours to use as you see fit and any airport is yours to use once above actual minima. Just don't land with less than final reserve if you want to avoid paperwork!