What are "Shalosh Delasos v'Arba'ah"?
Rashi citing Mo'ed Katan 26a: It was Megilas Kinos (Eichah). They read in front of him [the first four verses; their initial letters are Aleph, Beis, Gimel
Why does it say Shalosh (feminine) and "v'Arba'ah (masculine)?
Radak: It is because Delasos is a borrowed expression (they are not literally doors); it is feminine 1 .
Presumably, he teaches that we should not answer that Delet is both masculine and feminine; it is only feminine. (PF)
What is "Yikra'eha"?
Rashi: It is like Kar'ah (he tore it 1 ).
What is the grammatical form of "v'Hashlech"?
Radak: It is Makor (like an infinitive).
Why does it say "El ha'Esh Asher El ha'Ach"?
Radak: El is like Al. Later in this verse, it says "Al" regarding both of them.