Is it necessary to have the conscious intention not to return to the sin during repentance, or is awareness of the intention sufficient? And is the repentance valid if this conscious intention is forgotten for a long time?

If you find in your heart the resolve not to repeat the sin, along with regret and desistance, then your repentance is sound. Repentance cannot be imagined without the resolve not to repeat the sin. Rather, regret necessitates desistance and the resolve not to repeat the sin. Some scholars have stipulated that the resolve is a condition only if the thought of repeating the sin crosses one's mind.