Regarding manual increase of thrust levers above detent:
In SOME aircraft (dependant on mod status) if you are below 100' RA with the autothrust engaged and you nudge the levers above the detent, the autothrust will disconnect and you will get a huge increase in thrust as the engines chase the thrust lever position.
See FCOM 1.22.30 P62- subtlely hidden in the detail !
This will invariably lead to an unstable approach.
