Ecological succession

Both hydrarch and xerarch successions lead to medium water conditions, so all successions irrespective of the habitat proceed to a mesic climax community.

Primary succession begins where no living organisms ever existed: bare rock, newly created pond, newly cooled lava.
Secondary succession begins where natural communities have been destroyed, such as a degraded forest.

The stages of a hydrosere in order are: phytoplankton stage → rooted submerged plant stage → rooted floating and free-floating plant stage → reed-swamp stage → marsh-meadow stage → scrub (woodland) stage → forest (climax).
The second stage is therefore the submerged plant stage, occupied by plants such as $Hydrilla$ and $Vallisneria$.
$Azolla$ is a free-floating plant of the third stage.
$Typha$ belongs to the reed-swamp stage and $Salix$ to the woodland stage.
Hence the second stage is occupied by plants like $Vallisneria$.

Hydrarch succession takes place in wet areas, and the successional series progresses from hydric to mesic conditions.
Xerarch succession takes place in dry areas, and the series progresses from xeric to mesic conditions.
Thus both hydrarch and xerarch successions lead to medium water conditions (mesic), neither too dry (xeric) nor too wet (hydric).
The climax community in both cases is a mesic forest.
Hence both lead to medium water conditions.

Secondary succession begins in areas where the natural biotic communities have been destroyed, such as abandoned farm lands, burned or cut (deforested) forests and lands that have been flooded.
Because some soil or sediment is already present, it is faster than primary succession.
Succession that begins on a bare rock, where no living organisms ever existed, is primary succession.
It is not simply the same as primary succession at a faster pace: the starting conditions and the pioneer species are different, and it does not have to follow a primary succession.
Hence the correct statement is that it occurs on a deforested site.

A hydrosere is succession starting in water and ending in a mesic forest. Its stages are:
Phytoplankton stage (pioneers): e.g., $Volvox$
Submerged plant stage: e.g., $Hydrilla$
Submerged and free-floating plant stage: e.g., $Pistia$
Reed-swamp stage: e.g., $Scirpus$
Marsh-meadow and scrub stage: shrubs such as $Lantana$
Forest (climax) stage: trees such as oak
Correct sequence: $Volvox$ → $Hydrilla$ → $Pistia$ → $Scirpus$ → $Lantana$ → Oak