Any Catholic adult male is eligible, right?
CIC Can. 332 states for the one elected to be Pope: “If the person elected lacks episcopal character, however, he is to be ordained a bishop immediately.”
But to be a bishop:
CIC Can. 378 §1 To be a suitable candidate for the episcopate, a person must:
1° be outstanding in strong faith, good morals, piety, zeal for souls, wisdom, prudence and human virtues, and possess those other gifts which equip him to fulfill the office in question;
2° be held in good esteem;
3° be at least 35 years old;
4° be a priest ordained for at least five years;
5° hold a doctorate or at least a licentiate in sacred Scripture, theology or canon law, from an institute of higher studies approved by the Apostolic See, or at least be well versed in these disciplines.
§2 The definitive judgement on the suitability of the person to be promoted rests with the Apostolic See.
In practice the new Pope has been a bishop or cardinal. The last non-cardinal elected pope was Urban VI in 1379 A.D… From 1059 A.D. In Nomine Domini required that the new pontiff be selected from the Roman clergy, or if no suitable candidate can be found, the candidate can be chosen from another church.
The 2/3 majority is needed, except for an impasse, simple majority.