[Avodah] Cheilek LeOlam Habah/Impunity/Years

[Harvey Benton]

1. If someone explicitly tells Hashem that he would like to give up his Cheilek in Olam Haba to effectuate a desirable outcome, such as to Bring Moshiach, or to obtain a Refuah for someone, (or e.g., to obtain the healthy release of Gilad Shalit, etc), is such an arrangement valid and binding?  Such stories exist in Chasidic Literature, and as well in the famous story involving Rabbi Akiva and the Roman who was overseeing him being burned alive.

2.  If one has already given up his Cheilek LeOlam Habah, is he/she then able to act with impunity in those areas where one could subsequently lose that (already donated) Cheilek; e.g., Calling Someone by a derogatory Nickname, or Mevazeing someone (C"Veshalom) BePharhesia??

3. Similair questions as to validity of giving up years of one's life to someone else, e.g Adam Harishon to Dodid HaMelech.

Thanks Much, Harvey