If I give to a 2 shroud +3 from ancient stone I may commit two rise at ocassion even if my base is 3? How about 2 intelect 2 shroud double or nothing? If I use both to a 5 shroud and pass I may have 16 secrets on each stone ?

50 minutes ago, Veve7 said:

If I give to a 2 shroud +3 from ancient stone I may commit two rise at ocassion even if my base is 3?

Yes. The Investigate test is difficulty 5, and your base skill is 3, so Rise to the Occasion is legal.

51 minutes ago, Veve7 said:

How about 2 intelect 2 shroud double or nothing?

No. All skill cards are committed simultaneously; thus, even though the test eventually gets a difficulty of 4, it still has a difficulty of 2 when you choose which cards to commit.

54 minutes ago, Veve7 said:

If I use both to a 5 shroud and pass I may have 16 secrets on each stone ?

Yes (though I wouldn't recommend trying it). Using Ancient Stone I on a Shroud 5 location gets you a difficulty 8 test, and Double or Nothing doubles that to 16. Ancient Stone explicitly has you record the difficulty of the test, not the modified shroud of the location. Double or Nothing also means you record the result twice, but that doesn't actually do anything.

You're limited to 1 copy of Double or Nothing. The outcome of it would be to write that "you have identified the stone (X)" twice in your campaign log (which mechanically has no meaning). That sounds like a good way to raise the X (difficulty) value.

I can tell you from experience that Higher Education is a really good way to succeed at this test (assuming you have the resources & 5+ cards in hand).