The physical and chemical decay is not possible in vacuum but nuclear decay can neither be stopped.
No
not possible
Alpha decay requires two protons and two neutrons. Hydrogen only has one proton.
Thorium-232 is appearing in the thorium series.
No. Beta decay occurs when the Weak Force transforms a neutron to a proton or vice versa.
Any gas helps decay to occur.
The question is unclear. First before what? More likely to occur? I am going to assume the latter... Alpha decay is more likely to occur, when both alpha and beta are possible, because alpha decay removes more binding energy from the nuclide, and the tendency is to reduce energy as quickly as possible.
No
The only possible product of the alpha decay of 92238U is 90234Th.
not possible
no
fertilization
Not keeping your teeth clean and healthly
So you don't get smelly breath, and possible gum disease or other possible oral infections from tooth decay
Alpha decay requires two protons and two neutrons. Hydrogen only has one proton.
In a nuclear decay sequence it is possible for heavier atoms to decay to a lighter element.
Thorium-232 is appearing in the thorium series.