Does the unintentional browsing of sinful scenes constitute a breach of the oath I took on the Qur'an to abandon them, and how can I expiate this oath in Ramadan, knowing that I have not reached the age that permits me to feed the poor?

Repentance is an easy matter, yet it requires sincere struggle and seeking refuge in Allah. Therefore, you should associate with the righteous, attend circles of remembrance (dhikr), and strengthen your awareness of Allah's constant observation (muraqabah). No matter how often the sin is repeated, repeat your repentance, for "the one who repents from a sin is like one who has no sin." If you are unable to feed in expiation, then fast for three days, and do not fast them during Ramadan so that Ramadan can be dedicated to the obligatory fast. Regarding your second oath, refer to your intention; if you had no intention, then refer to the reason for the oath; otherwise, refer to the apparent meaning of the wording. The basic principle is that there is no violation of the oath when in doubt.