MB3 102b: Borrowing and Repaying on Shabbos (307:9-12)

When can you go to the edge of the Techum on Shabbos afternoon? What if it's recognizable that you are going to do something that would be asur on Shabbos. Borrowing something on Shabbos for a long period of time & returning it on Shabbos. Taking collateral on Shabbos. Reading a memo/reminder you wrote before Shabbos.