I am not clear on exactly what you want. I'll start with this in B11 of your Form sheet.
Formula:
=IF(DATE(YEAR($B$10),MONTH($B$10)+ROWS($1:1),DAY($B$10))<INDEX(Data1!$D$4:$D$8,MATCH(Form!$F$3,Data1!$A$4:$A$8,0)),DATE(YEAR($B$10),MONTH($B$10)+ROWS($1:1),DAY($B$10)),"")
Fill down. Then this in D11 and fill down.
Formula:
=IF(($B11<>"")*($B11<>0),$F$5,"")
These will auto-populate, but I am not sure this is how you want it to happen.
By the way the uploaded workbook had calculation set to Manual. I changed it to get the formulas to work.
Workbook is attached.
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