20 b bottom - lands conquered by king can be given to Kohanim and Leviim. See Rambam 4:10, Dvar Moshe 191. Abarbanel Shoftim.
21a - taama d;kra or not. Why not say like Tos Sukkah 6 that the same tana sometimes holds yesh eim l'mikra and sometimes yesh eim l'masors?
Rashi sv mi hava. Implies had she converted before the borth there would be korva. But conception was as a non-Jew so why would there have been korva? Ot's horasa shelo bikdusha!
Lo s'ar beis hashechi. Navi said it was punishment. But how did these genetic changes happen? Kuzari - part of our dna that we can change, adapt looks / physical characteristics of the nations among who we live. 2) from converts introducing other genes into the gene pool
21b Rashi sv lo nisgalu. Why does he only mention Chukim? And see Margolios hayam.
Rash isv al hayichud. Clearly gemara later changes it to al hayu=ichud d'pnuya. But how can Rashi say yichud Eishes ish was decreed then? It was earlier! And Tosfos later, 37a, clearly says that!
Rashi Aspania. This is leshitaso earlier on 18b that king paid soldiers by the year. But Aruch (see margin there) says it is paid month by month.