Can these changes be reversed by changing temperature?
Both processes involved the denaturation of proteins and complex reactions so is impossible reverse them only with a change of temperature.

Boiling an Egg
Although in most case denaturation is not reversible there are some cases where it is.
However in the case of Egg white denaturation is irreversible (see here) and so the whole process is by the way irreversible.
Cooking batter
The same for the batter even if is unclear which flours are used, and the composition of the batter  you can be sure that after cooking batter on a hot griddle surely some irreversible reactions occur: denaturation, Maillard reaction, Amadori rearrangment.