[Mesorah] Davening: Pesach vs. Hag Hammatzos

[R. Rich Wolpoe]

In Tanach Hag Hammatzos
Starts the 15th of Nissan [Hodesh Harishon]

Pesach starts the 14th of Nissan

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In Talmud Pesach often appears to replace Hag Hammatzos.  

Q1:  Is Pesach L'shon Hazzal for the Holiday

Q2:  Is there a reason that the liturgy seems to favor L'shon Tanach over L'shon Hazzal for the Amidah for example?
Shalom and Regards, RRW