snail-astroceras
snail-bellerophina
snail-euhoplites
snail-hörnlischnecke
snail-mya-araneria
snail-natica-stellata
snail-pseudoheliceras-subcatenatum
snail-turitella
aeskulap
amphore
apple
astroid-torus
beauty-shell
bell
bent-horns
bohemian-dome
bonan-Jeener-Klein
bonbon-helix-I
bonbon-helix-II
borromean-rings
bow-curve
bowl
boys_apery
boys
braided-torus
breather-2
breather-surface
circled-helicoid
cornus
cosinus-surface
cross-cup
curvefield
dna
donut
double-cornus
drop
dupin-cyclide
egg-perfect
elipsoid
enneper-five
enneper
feather
fish
flower
folium
form-moebius
gnocci
henneberg-surface
hexahedron

If you were following the instruction you should see the new objects. But in some cases you have an individual user settings. Try to search for the right path with the explorer/ finder. Sometimes you find maybe the path of a different Blender Version, if you work with multiple Versions. So be aware to be in the right folder.

No, once primitives or object are created by operator, their parameters can no longer be accessed. But if you look for my other Product, you´ll find a Geometry node Version. There you have the possibility to make changes after you have created the Object. They are all Non-destructive