Using CSV cell values to reference a table and return matches in CSV format in new cell

This proposed solutions employs 20 helper columns, XEK:XFD, on sheet2.
The formula for column XEU is: =LEFT(B2,SEARCH(",",B2)-1)
The formula for columns XEK:XET is: =IF(XEK2="","",IFERROR(MID($B2,SEARCH(",",$B2,SEARCH(XEK2,$B2))+1,SEARCH(",",$B2,SEARCH(XEK2,$B2)+1)-SEARCH(XEK2,$B2)),""))
The formula for columns XEU:XFC is: =IFERROR(INDEX(Sheet1!$B$1:$B$12,MATCH(VALUE(XEK2),Sheet1!$A$1:$A$12,0))&IF(XEL2<>"",",",""),"")
The formula for columns XFD is: =IFERROR(INDEX(Sheet1!$B$1:$B$12,MATCH(VALUE(XET2),Sheet1!$A$1:$A$12,0)),"")
The formula for column C is: =CONCATENATE(XEU2,XEV2,XEW2,XEX2,XEY2,XEZ2,XFA2,XFB2,XFC2,XFD2)
Let us know if you have any questions.