What is the format of newly imported file into the Adobe Premiere project? Evenmore, will the video be lossy encoded?
Premiere works with the source files you provide. Depending on the format it may generate a lossy copy that can be used for faster preview in the editor, but final renders will work directly from your source files. That's what's going on if you see it says it is conforming files in the lower right corner.
Check the supported video formats of Adobe Premiere here. And i don't think it would loss some video quality because it's very powerful and professional, that's one of the reasons why people like to spend such much money for it.