$1.$ Does oxidisation mean formation of oxides or the loss of electrons in the reaction eg$.$ OXIDATION IN PHOTOCATALYSIS

$2.$ Hydrogen storage tech : I know of hydrogen technologies like :

compressed tank $($ I.e cryogenic$),$ chemical sorbent, metal hydride and liquid H$2($ cryo$)$

Except these are there any other RECENT NEW RESEARCH technology for Hydrogen storage? If yes $,$ what and Plz explain in detail

$3.$ What is dark fermentation $($ difference in compare to photosynthesis$)$

$4.$ How does photocatalysis by solar p$.$v happen and work? Plz explain I$\text{'}$m detail

$5.$ Does iron rusting have loss of electrons? And that leads to rust or formation of oxides? Yes or no$?$