(a) megilla 27--how does the gemara handle the issue of tzad echad bribis is issur---when it comes to the parsha of batei areyi choma in v'yikra---sounds like the purchaser of the house has the same preoblem is the house is repurchased within the year
(b) megilla 27--the gemara questions and leaves unresoved the issue of exchanging an old siefer torah for a new one---if the old sefer tora is pasul and un-fixable, would onre be able to sell the old and buy a new one---what is the kedusha level of the old sefer torah
(a) That is true, as the Gemara in Erchin (31a) points out. The Gemara there answers that it is a Gezeiras ha'Kasuv.
(b) See what we wrote in the Insights to that Daf.