This note is merely a potsherd - האי שטרא חספא בעלמא הוא
Summary:
When the גזלן purchases the field from the נגזל it is transferred immediately and automatically to the לוקח (without any other קנינים). A קנין can be accomplished though הנאת מחילת מלוה, however it cannot be accomplished (by מכר) through מחילת מלוה (according to one view of תוספות).
Summary:
If we maintain אדם מקנה דשלב"ל, either party can retract when it is still לא בא לעולם (regardless if מעכשיו was said or not). If the קנין of a דשלב"ל was made with a שטר and the שטר does not exist when the item is בא לעולם, there will be no effective קנין, unless מעכשיו was mentioned originally.